Moses Ludel
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Posts posted by Moses Ludel
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Well, I'm not sure what your original motive was for the disc rear brake conversion, but the findings are not that surprising. Brake bias is to the front, and your Jeep CJ-7 has adequate factory disc brakes there. The drum rear brakes on a later CJ-7 were also sufficient for most uses. Are you satisfied that the brake apply pressure is sufficient at the rear brakes?
Let's put some rays of sunshine into your effort around this 8.8" rear disc brake conversion. Since you went ahead and did it, the positive gains should be considered. For openers, disc brakes have several trail use advantages over drum brakes:
1) Resistance to fade in hard rock crawling and continual application of the brakes; this also applies to trailering.
2) Ability to immediately work well after crossing a stream, with less risk of damaged parts from water crossings.
3) Winter benefits over drum brakes (RareCJ8 laments his drum rear brakes); less risk of frozen parts or ice lock-up when parked.
4) Ease of service around pad changes; calipers are accessible.
5) Easier visual inspection for wear or defects; troubleshooting is quick and simple.
6) You have a contemporary brake system (8.8" Ford) with easy parts availability on a weekend—or in the middle of Podunk.
What was the source/application for these rear disc brakes? I'd like to compare the OEM bore diameters between your CJ-7 master cylinder and the Ford application's master cylinder. To be completely fair about the effectiveness of the "new" disc rear brakes, let's determine whether the CJ-7 master cylinder is applying the same pressure to these rear calipers as the Ford OEM master cylinder.
Again, your findings are not unusual. Rear braking on a late CJ-7 can be readily met with OEM drum brakes. Now, if you had the '55 Jeep CJ-5 featured in my Jeep CJ Rebuilder's Manual 1946-71 Edition, that would be another story. 9" x 1-3/4" brakes are inadequate, front or rear, by any standard! I've often noted, however, that 11" x 2" drum brake conversions work very well on the early Jeep CJ and military models. While disc brakes have many advantages, effective rear braking can be met, most of the time, with sufficiently sized drums and brake shoes.
Moses
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Thanks, I thought this info might be useful, folks often mix up parts in an effort to save cost and avoid expensive disc brake conversion "kit" approaches...
I got the visual on "cement" mud around the huge brake drums or slushy freeze-ups in the winter! Those massive rear drum brakes on a CJ-8 Jeep Scrambler should be overkill, for sure. If you're using the stock master cylinder, there is likely less rear brake apply pressure than with a Ford E-van master cylinder. You can compare master cylinder bore diameters to get a better sense for this.
There's also the concern around too much braking capacity at the rear. Your 10.25" Sterling axle is designed for a high gross weight application (E-van), and you might find that OEM discs for that kind of rear axle would provide too much braking force. The front axle and disc brakes are 3/4-ton capacity truck, right?
When the time comes, we can kick around details on braking capacities for available front and rear brakes. What you want to avoid is "over-braking" at the rear, as rear lockup or bias can cause a vehicle to spin out, especially on loose or slick surfaces at speed. A classic stunt driving trick is to apply the rear parking/emergency brake on a very slick surface, without touching the brake pedal. The effect is dramatic: The vehicle immediately spins around. (Caution: Do not attempt this trick unless you're on a professional, slick skid pad. Uncontrolled, it can be very dangerous and even cause a vehicle rollover.)
Spinout can occur with an over-braking bias toward the rear of the vehicle. Driving on an icy highway or slick trail, especially a downgrade, could be a recipe for disaster if you need to stop quickly. One way to offset this bias is use of a manual brake proportioning or metering valve, adjusted to reduce brake apply pressure at the rear.
Some trucks even incorporate an OEM manual brake proportioning valve at the rear axle. Activated by a mechanical lever arm, the valve reduces brake apply pressure when the vehicle's rear end gets light (springs extend) during hard braking with front end dive. We had K2500 GMC Suburban 4x4s from the mid- to late-'80s that had this feature...
We can discuss all of this further...Have a safe, fun 4th of July RareCJ8!
Moses
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Umm...On the suction side, a larger orifice would lift more fuel, and that could be a liability. Fuel is mass and volume, and the pump motor would work harder moving the higher volume of fuel, especially as the pump first starts its cycle.
On the push side of the pump, they want the larger hose to prevent any restriction. Volume gets controlled by the pressure regulator at the EFI rail. In your two-rail system, the excess goes back to the tank. If you use a larger pickup hose, there could be more volume going back to the tank.
There may be a sound engineering reason for that 5/16" inlet. Is it impractical or difficult to use a 5/16" pickup hose to the pump and 3/8" to the rail?
Moses
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There are many times when a pinpoint reading of brake hydraulic pressure is useful. Brake safety and vehicle handling require the right hydraulic force at each wheel of the vehicle—at the right time! Knowing precisely how much apply pressure is available at the master cylinder, combination valve, ABS system, wheel cylinders or disc brake calipers can help troubleshoot weak brakes, grabby brakes, brake pull, erratic handling under hard braking, hazardous wheel lock-up and more.
Whether you tackle your own vehicle service or operate a 4x4, OHV or motorcycle shop that depends on customer satisfaction, one valuable tool for brake system diagnostics is a hydraulic pressure tester. Maybe you're installing a retrofit rear disc brake upgrade like some of our forum members. Or you put oversized tires on your 4x4 and now a major braking issue has developed...If you take brake work seriously or find yourself in need of pinpoint information on a brake system's performance, consider a hydraulic brake and ABS diagnostic tool kit like this:
This tool kit can pay for itself quickly in pinpoint hydraulic brake system diagnosis. Click on images to enlarge.
(If you cannot see the pictures, join the forums for free, and get full member access!)
I find this tool valuable. You can separate hydraulic problems from mechanical issues, or ABS issues from defects in rotors, brake drums and friction materials. With the assortment of fittings, the kit can work on most domestic and import vehicles.
If you're having trouble separating brake performance issues, don't waste time and money on parts replacing that fails to solve problems...Take the guesswork out of brake work. Know how the hydraulic system performs before you leave the shop or driveway—not by trial and error. Invest in the right diagnostic tools!
Moses
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Disc brake conversions are popular, and I cover that topic in my Jeep CJ Rebuilder's Manuals (1946-71 and 1972-86 Editions, Bentley Publishers). Whether the CJ has a four-drum system or a disc front/drum rear system, the master cylinder must be considered during a disc brake conversion.
There are two master cylinder concerns when converting to disc brakes: 1) the piston bore size and fluid volume per stroke of the pedal and 2) any "residual valves" that might have been used for the drum brakes. For disc brakes to work, the master cylinder must have enough fluid displacement to apply the calipers and pads. Disc calipers use more brake fluid per pedal stroke than properly adjusted drum brakes.
If the Jeep is a vintage CJ 4x4 with a single master cylinder and drum brakes, especially the 9-inch diameter drum system, the stock master cylinder will be inadequate for modern disc brake calipers. Drum or disc brakes, I'd want to get rid of the single master cylinder for safety sake, regardless!
In converting to disc brakes, the best choice here should be a modern four-wheel disc brake type dual master cylinder retrofit. A retrofit can even be done using the original, through-the-floor brake pedal, as I illustrate in the 1946-71 Jeep CJ Rebuilder's Manual (Bentley Publishers). I fabricated a safe, sturdy mount for a later dual master cylinder—mounted beneath the floorboard like the stock master cylinder and actuated by the stock brake pedal.
Sometimes, a disc/drum master cylinder will have adequate fluid displacement on the rear drum circuit to operate retrofit disc rear brakes. Again, this depends on the master cylinder's bore size and stroke per pedal application. The rear fluid reservoir is often smaller, so keep fluid at the recommended full level.
On 1972-up Jeep CJs with four-wheel drum or disc front/drum rear brakes, you may be able to use the stock master cylinder with a disc brake conversion. Be aware, though, that some master cylinders will require removal of the residual valve(s) from the master cylinder ports.
The "residual valve" is important on many drum brake systems. To keep the wheel cylinder cup lips expanded, which prevents fluid seepage from the wheel cylinder with the brakes released, a valve is built into the hydraulic system to hold "residual pressure" in the wheel cylinders when the brakes are released. Early single master cylinders and many four-wheel drum or disc/drum dual master cylinders have built-in "check" or "residual" valves.
This residual pressure is below the tension of the brake shoe return springs. Residual pressure is simply to keep the wheel cylinders from drawing air or leaking fluid when the brakes are released. This pressure is typically around 12 PSI, well below brake shoe return spring tension.
By design, disc brake calipers do not require residual pressure. The pads release pressure with the pedal release. There is adequate fluid available in the circuit to apply the brakes without lag or hesitation.
Some disc brake hydraulic systems, do have very slight residual pressure to keep the pads close to the rotors at all times and improve brake response time during pedal application. This pressure would be around 2 PSI and not enough to cause premature pad wear, fade or overheated rotors.
Note: If you're using a four-wheel drum or disc/drum CJ master cylinder, check the fluid line ports for a residual valve. Typically, this valve is simply a rubber plunger and balance spring at the back side of the tubing flare nut seat. With the brake lines removed from the master cylinder, you can see the rubber plunger through the passageway at the center of the tubing flare nut seat. This seat is removable for service and seat replacement. If you are curious how to safely remove the seat, I'd be happy to detail—ask here at the forum!
Caution: When retrofitting from drum to disc brakes, you need to remove the drum brake residual valve(s). Earlier Jeep dual master cylinders for four-wheel drum brakes have residual valves at both the front and rear fluid line ports. OEM disc/drum brake systems can have a residual valve on the rear brake circuit. If the residual valve for drum brakes is left in place, the disc brake pads will drag on the rotors with the brake pedal released. This can cause excessive pad wear, brake fade and even wheel lockup.
One disc brake conversion example is our fellow forum member "LastCJ7". He has a 1986 CJ-7 Jeep (disc front/drum rear factory brakes) and is converting to rear disc brakes. He's trying the CJ-7 dual master cylinder before considering a late Jeep TJ Wrangler Rubicon (four-wheel disc from the factory) master cylinder...LastCJ7 needs to make sure there is no residual valve holding pressure in the rear brake system with the brake pedal released.
On later disc/drum master cylinders, there may not be a residual valve in the rear brake circuit. Many manufacturers have changed over to stiffer wheel cylinder cup expander springs with sturdier cup expanders. This measure keeps the rubber cups expanded with the brakes released and serves the same purpose as older residual valve systems.
When converting to disc brakes, explore whether your original dual master cylinder uses a residual valve or valves. Vintage, single master cylinders have a check valve within the master cylinder to hold residual pressure in the system—one more reason why a single master cylinder is not a candidate for a disc brake conversion!
Make sure the master cylinder's fluid displacement (per pedal stroke) will meet disc brake caliper requirements. If in doubt, retrofit a combination valve and master cylinder from a similar chassis—like retrofitting a Jeep TJ Wrangler Rubicon master cylinder and combination valve to a CJ-7 chassis.
Summing up, make sure the brake hydraulic system is compatible with the disc brake calipers and rotors. Both the CJ-7 and TJ Rubicon are on a 94" wheelbase, each has beam axles and an inline six-cylinder engine, their curb weight is a close match, so they should have similar braking needs and characteristics...Jeep TJ Wrangler Rubicon brake components would be a good template for the CJ-7 wheelbase and four-wheel disc brakes.
Moses
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Curious to see how this works out with the full brake bleed. Comes down to whether you'll get enough stroke/fluid volume at the rear brake circuit while using a CJ-7 master cylinder. You need enough fluid per pedal stroke and adequate apply pressure at both the front and rear calipers. If this is not the case, consider the TJ Wrangler Rubicon four-wheel disc brake master cylinder!
On another note, if you're using your disc/drum CJ-7 master cylinder, make sure there is no residual valve on the rear brake hydraulic circuit. Otherwise, the rear brake pads will drag on the rotors with the pedal released, causing quick pad wear, brake fade or even wheel lockup. This step is often overlooked on rear disc conversions. I've opened a new "topic" on this important safety subject. See this discussion begin at http://www.4wdmechanix.com/forums/index.php/topic/110-rear-disc-brake-conversions-master-cylinder-needs-and-the-drum-brake-residual-pressure-valves/.
I'm taking photos of the brake pressure test equipment and will post at the tools forum...4x4 owners who work on their vehicles and professional techs will appreciate this diagnostic tool.
Have a safe, fun 4th of July holiday. Looking forward to the update on your Jeep CJ-7 four-wheel disc brakes.
Moses
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The exchange with Megatron around his 48RE shudder at take-off reminded me of installation of oversized tires on our Ram 3500 4WD truck. Prior to installing the 4" lift and oversized tires, the truck had achieved great fuel mileage as a stone stock vehicle.
I was thrilled with the Ram's fuel mileage and performance from new (October 2004) until the summer of 2011. Then it was time to bring the truck to the standard that readers and sponsors like—lifted, accessorized and sporting oversize tires! (See the Ram truck build up at the magazine: http://www.4wdmechanix.com/2005-Dodge-Ram-3500-Major-Makeover.html.)
Stock gearing was 3.73:1, and with a Cummins 5.9L ISB engine, that meant cruising between 1,600 and 1,900 rpm most of the time. This worked perfectly for fuel efficiency, much to Chrysler's engineering credit. My expectation, considering the extraordinary low-end torque of the H.O. diesel, was that oversized tires would have little impact on the fuel mileage—in fact, I even speculated that the mileage would improve, since the engine could stay in the 1,600 to 1,700 rpm range at interstate speeds! Peak torque for this engine is at 1,600 rpm, optimal for fuel efficiency.
Boy, was I in for a surprise! Trips to Chico, CA for the Transfer Flow fuel tank installation and the subsequent run to the 2011 Off-Road Expo at Pomona gave a hint. Mileage seemed stagnant and, if anything, off its usual peaks. I attributed the unimpressive mileage to mountainous roads and higher cruising speeds, but the true problem reared itself when I towed a 7,500# toy hauler trailer to the 2012 King of the Hammers Race at Johnson Valley, CA. The trip was to film the races and interview celebrities like Shannon Campbell that week. (You'll find this coverage and more at the 4WD Rock Crawling & Racing Channel on the magazine website.)
Trailer in tow to places like Moab, UT, the truck had achieved 17 mpg at interstate speeds and 6% grades with the stock diameter tires (under 32" diameter). Now, with 35" tires, the mileage with the same weight trailer in tow, adhering to California's trailering speed of 55 mph, the mileage plummeted to 12-13 mpg! Before all of the modifications and weighty accessories, at 55 mph with the stock tires and gearing, trailer towing would have netted 19-20 mpg!
Oversized tires with stock gearing creates an additional "overdriving effect". Sometimes this is advantageous, but in the case of our '05 Dodge Ram 3500 4x4 Quad Cab, the combination of 1,350 pounds of new accessories and auxiliary fuel, plus the 35" tires, made the stock 3.73:1 gearing unacceptable.
The change to 4.56:1 gearing has bumped fuel efficiency back to a peak of 21-23 mpg (unloaded, full fuel capacity, no trailer in tow)—if I keep speed at or below 65 mph in overdrive. While a direct correction for the tire size and axle gearing would have been 4.10:1, I knew that the added weight of accessories and auxiliary fuel, plus the increased drag from the lift, would make "stock" gearing no longer practical.
With the 4.56:1 gears, I do "pay for it" in extra fuel consumption when driving above 65 mph. It acts like a linear thing: The fuel mileage drops with each mph increase in speed! Had I planned on driving over 65 in overdrive most of the time, without a trailer in tow, I would have opted for the 4.10:1 gears. We do plan to pull trailers with a GVWR under 10,000#, so the 4.56:1 gears are optimal, and mileage is good—if I keep my foot out of the throttle!
If you own a Ram 2500 or 3500 HD 4WD pickup like ours, a suspension lift and oversized tires will likely demand ring-and-pinion gear changes. I cover the 11.5" and 9.25" AAM axle re-gearing at the magazine site:
http://www.4wdmechanix.com/How-to-AAM-11.5-Axle-Rebuild.html [detailed article with how-to steps in color photos]
http://www.4wdmechanix.com/HD-Video-How-to-AAM-9.25-Axle-Rebuild.html [an overview that works in conjunction with the 11.5" AAM axle rebuild article]
Moses
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You described your take-off shudder well. For openers, this is not likely converter related, as the converter clutch is not active at this speed. If it is the converter, this means the converter clutch is dragging, in which case the symptoms would get steadily worse and cook the converter. If you do suspect the converter, I can share how to test it in the truck.
Some would jump to transmission issues like band adjustment or worn clutch packs, motor mount issues, with the Cummins especially, and surely this could contribute. Likely you have done the band adjustment during service work, though. There would also be a benefit to upgrading to the aluminum accumulator piston that I describe and install in my Sonnax survival upgrades. See that article at: http://www.4wdmechanix.com/Survival-Upgrades-for-Jeep-and-Dodge-Ram-Automatic-Transmissions.html. You'll see the accumulator piston change there, too.
I like your gut comparison to the Ford Powerstroke that lost its clutch and flywheel harmonic dampening with the solid flywheel and clutch install. You may have a similar harmonic or actual binding issue with the shudder you describe. This may come as a surprise, but I would look elsewhere for that load shudder when you get the truck moving: check the rear driveline/U-joint angles. You have a 6-inch lift on the truck, and I'll share some pointers here.
Your Mega Cab wheelbase likely uses the two-piece driveshaft. If so, the shaft from the transfer case to mid-shaft bearing is probably stock still. Maybe you've dropped the mid-shaft bearing to reduce driveline angle at the rear piece. In any case, the U-joint angles must "cancel each other", meaning that an angle at the transfer case should have the same cancellation angle at the other end.
A common issue with taller lifts is to not have the joint angles cancel properly. For example, there may be a straight shaft out of the transfer case and through the mid-shaft bearing. If so, the angle of the second/rear driveline should have U-joint angles that cancel each other (complementary angles) on the second or rear shaft.
Many think it's great to angle or rotate the rear axle pinion upward to reduce pinion joint angle. That only works if the angle either 1) matches the angle complement at the other end of the shaft (which is impossible) or 2) the front end of the shaft uses a double-Cardan or CV type joint as seen in the photo below. Also see this Jeep XJ Cherokee article at the magazine for a single piece driveline and 6-inch long arm lift:
As a final note, you have shared that you're still running 3.73 axle gearing with the 37" oversized tires. This is enough to cause extreme take-off loads and maybe even the shudder you describe. The 3.73:1 gearing is marginal even with the factory tire diameters of less than 32". At your current ratios, the gearing is way out of balance.
Moses
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Thanks for the compliment, Megatron...I get academic and like to research procedures and options before tackling a project. This habit was firmly in place long before I became an automotive and truck journalist—or wrote seven Bentley Publishers automotive and motorcycle books...I believe it's important to diagnose and pinpoint an issue before replacing parts.
As we address the 48RE, let's share and compare findings. At this stage, a full rebuild seems many miles away on our unit. If and when I do go deeply into our transmission, it will likely be a "how-to" in either article or video format for the magazine, something like what I did with the AAM 11.5" and 9.25" axle builds.
If you dive into your transmission earlier than that, I'm here to answer questions.
Moses
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Keep us posted, and keep my comments in mind if the results are not what you expect...Vacuum bleeding would be a good idea with the easy-out metal debris.
Here for more questions!
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Thanks for the thorough, thoughtful reply, Megatron...I'll jump in on your comments, it would be great if others would join, too!
As for history, the RWD Chrysler A727 Torqueflite transmission has seen a lot of severe service and so has its overdrive A518 and 42RE to 48RE truck derivatives! By the time our trucks were built, Chrysler boasted that the 48RE was the best unit every produced and a match for the H.O. Cummins output—I remember this from advertising materials when we bought the '05 Ram 3500. Of course, the later A580 5-speed and 5/6 speed transmissions became the Chrysler buzz when they were released.
That said, there is a flourishing aftermarket industry around parts for the 47RE and 48RE units. From torque converters to billet input shafts, valve body upgrades, solenoid kits, Sonnax survival items and so forth, one would quickly get the impression that this transmission was marginal from the start. That's not altogether true, though, as many of these upgrades are for radically modified, Cummins "pullers" and heavy-duty trailer haulers. Every other truck manufacturer has a laundry list of automatic transmission weaknesses to its credit—a trip to the Sonnax website uncovers an industry-wide, OEM epidemic of automatic transmission weaknesses and issues.
So let's start with a basic look at the 48RE four-speed overdrive, which shares architecture with the A727 three-speed that dates back to 1962. After doing similar homework to yours, Megatron, I concluded that if I took horse trailer pulling seriously, or pulled a 36-foot travel trailer (conventional, non-5th wheel type, as I have no bed space in the 6.3' bed with a cross bed auxiliary fuel tank), I'd have the 48RE out of the truck and on my work bench—in a heartbeat!
I would install a billet input shaft, Banks or BD torque converter, the heavy clutch and drum kits, improved bearings and thrusts, better band materials and friction clutch plates, a strut improvement plus any planetary improvements available. Then I'd add a cooler system like you describe!
I'm not building a competition puller with 800 horsepower, though, and there is a "middle road" for 48RE survival. The aim is the kind of reliability that would see our truck up and down the Alaska Highway with a 27-foot travel trailer in tow. Moderate survival measures can, as we share, be as simple as in-chassis valve body improvements, a better strut and accumulator piston (see my Sonnax upgrade article), and if removing the transmission is acceptable, at least the addition of a torque converter that will stay together.
At an even more basic level, I do have an interesting quirk that developed with the Sonnax upgrades to the valve body and accumulator piston. To keep from boring readers to tears here, I'll simply refer folks to the Sonnax upgrades article at the magazine for details: http://www.4wdmechanix.com/Survival-Upgrades-for-Jeep-and-Dodge-Ram-Automatic-Transmissions.html.
The quirk is the downshift to first gear after the transmission warms up. As you describe, there is an epidemic of solenoid issues around the RE transmissions, and the governor can also come into play on downshifting problems. The issue in this case is a hard downshift to first gear as the vehicle comes to a stop. This never occurred before the upgrades, and we purchased the truck new.
No, it's not ABS related. I clocked and calibrated the speedometer to compensate for the oversized tires, using a factory DRB III scan tool. For those interested in speedometer calibration, I cover this procedure in an HD video at the magazine site. See the 4WD Tech How-to Channel coverage: http://www.4wdmechanix.com/How-to-Dodge-Ram-Speedometer-Calibration.html.
If I come to a stop slowly, the transmission will slide somewhat "normally" into first gear. An abrupt stop can sometimes mask the hard downshift, too. But if I stop the truck at the usual pace, the downshift with the transmission warmed up will be harsh. Worth noting, there is no such symptom whatsoever when the transmission is cold.
At first, the internet scuttle had me thinking in terms of solenoids, but my instincts and experience suggested otherwise. I trained as an "Automatic Transmission Specialist" in 1969 and have rebuilt and restored everything from the Dynaflow (Buick), Hydra-Matic (big G.M. and GMC truck) and Packard Ultramatic transmissions to the modern overdrive and "electronic" truck units.
Our 48RE transmission shifts flawlessly when first started and driven for several miles—smooth up and down through the ranges and gears. It's only when the unit warms up that there is a downshift issue to first gear. All other shifts, up and down, are fine at all times, including the rollover to overdrive under heavy load. As a footnote, I adjusted the bands by the book and even rechecked these adjustments.
I tossed this topic to Mitch from Hughes Performance transmissions when we met at the SEMA MPMC Media Trade Conference in January. Mitch thought the problem could be the transmission cooler, clogged in his view. At the time, I thought about this on the 500 mile drive home...He could be right about clogging, especially when I consider the healthier line pressure from the Sonnax upgrades. There's also the thermostatic switch on the OEM cooler.
The OEM cooler in front of the radiator has a thermostat that bypasses fluid when the transmission is cold. As the transmission warms, the thermostat redirects pressurized fluid through the cooler. If the cooler were clogged, as Mitch suggested, the thermostat would force fluid into a restricted cooler. Could the harsh downshift be related to this? If so, it would be due to the back pressure boost at the governor, solenoids and valve body passageways.
Not a bad theory, and I'm somewhat buying the idea. After all, the transmission shifts up and down flawlessly when the thermostat has the fluid bypassing the cooler. I'd like to think that the trans cooler (OEM) would not clog in 90K miles, the time when I did the Sonnax upgrades. Who knows, though. If the cooler is at marginal capacity to begin with, it's possible that clogging or even the stock volume flow would create a problem with the improved fluid flow...
That's why I tossed out my question about eliminating the thermostat in the process of upgrading the transmission cooler. If anyone has an opinion about this, I'd like to hear it. I will look at the Fleece Performance cooler, Megatron. In fact, I'll likely call them, as I'd like a firsthand sense for why their approach is an improvement.
I'm totally on board with your heat/death cycle projections for automatic transmissions, old enough to remember the original Hayden add-on cooler data from the 'sixties. I was solely responsible for a 22-vehicle fleet of light- and medium-duty trucks when I did my automatic transmission certification—add-on coolers were popular then and have been ever since!
There are also the Amsoil and Mobil 1 ATF pitches from the day, emphasizing a 50-degree F drop in automatic transmission temperature through the use of synthetic ATF. That claim is real and accounts for Chrysler's progression from ATF-2 to ATF-3 to ATF-4, now a synthetic and specially formulated fluid intended to keep a modern automatic transmission alive. This is in step with your comments, Megatron. OEMs have turned to synthetic fluid and additives to get their transmissions through warranty period.
So, before I start condemning solenoids or the governor, I'll make certain that the transmission cooler is not causing a pressure spike on coast down that creates a harsh downshift to first gear. If I have an issue after that, be assured, I won't rest until the problem is resolved—by yours truly, as I'm the only one who works on my truck, especially the automatic transmission...Expect an update!
Moses
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Very well-equipped Jeep CJ-7 4x4, "LastCJ7"! Interesting brake system, trust all safety concerns were addressed with the alignment and fit of the rotors and calipers. There is huge rotational force with braking, and the wheel studs, rotors and caliper mounting brackets must each follow OEM engineering principles and material standards. Presumably, you did your homework here...Is this a proven and safe conversion?
Sounds like the issue with the proportioning valve could be proper bleeding technique for the '05 Rubicon type valve. We'll address that, as you likely do not have fluid pressure at the rear brakes from what you describe. Before bleeding properly, though, I'll comment on your other two questions.
Regarding the mounting point for the proportioning valve, either position would work. Since pressure from the master cylinder to the valve remains uniform, the location should not be an issue. When the master cylinder bore is not “stepped”, the line pressure would actually be equal on each sub-system (front and rear brakes), at least from the master cylinder to the proportioning valve. Sometimes the master cylinder bore is stepped in size, in which case the line pressure leaving the master cylinder differs per line.
Many manufacturers mount the proportioning valve at the frame, directly below the master cylinder. The idea is to make it accessible, especially for bleeding or centralizing the safety switchover valve (a time-honored, challenging feature on later Jeep CJ braking systems). You likely have encountered the combination valve bleeding issue with your stock brake system. On your original CJ-7 combination valve, a special tool holds the switchover valve in position during the bleeding procedure.
Your '05 Rubicon proportioning valve is designed for a four-wheel disc brake system. It was also intended for the Rubicon master cylinder, which delivers the correct volume of brake fluid to the front and rear. In considering master cylinders, it's worth noting that disc brake caliper pistons typically require more fluid volume to actuate than drum brake wheel cylinders. Note that the master cylinder reservoir for disc front brakes/drum rear has a larger front brake reservoir, reflecting the need for more fluid displacement during the braking process.
It's unclear whether your rear disc brakes are getting enough fluid volume, and that's something you need to determine. If there is an issue with the master cylinder's per stroke fluid displacement and not enough brake fluid to the rear brakes, the rear calipers will not apply properly. You would need to retrofit something like the Rubicon master cylinder to remedy that problem.
If you determine that the rear brakes do not get enough brake fluid volume with your CJ-7 master cylinder and decide to use a Rubicon master cylinder, be sure you mount the retrofit cylinder properly. The master cylinder piston must fully retract with the brake pedal released! If the pedal height is wrong or the power booster pushrod is too long, the brake master cylinder piston will stay in a partially applied position. If the master cylinder piston is either blocking or past the compensating port(s), this can trap fluid in the brake system and cause brake drag or even wheel lockup.
If bleeding the system does not resolve the rear brake apply issue, and you're certain that fluid under pressure is reaching the rear brakes, then you do have a fluid displacement problem: too little fluid volume per pedal stroke to actuate the rear brake calipers.
What you're calling the proportioning valve is actually a "combination valve". Here are 2005 Jeep TJ Wrangler factory designated combination valve functions:
"The combination valve contains a pressure differential valve and switch and a rear brake proportioning valve. The valve is not repairable and must be replaced as an assembly if diagnosis indicates this is necessary...The pressure differential switch is connected to the brake warning light. The switch is actuated by movement of the switch valve. The switch monitors fluid pressure in the separate front/rear brake hydraulic circuits...A decrease or loss of fluid pressure in either hydraulic circuit will cause the switch valve to shuttle to the low pressure side. Movement of the valve pushes the switch plunger upward. This action closes the switch internal contacts completing the electrical circuit to the red warning light. The switch valve will remain in an actuated position until repairs to the brake system are made...The proportioning valve is used to balance front/rear brake action at high decelerations. The valve allows normal fluid flow during moderate braking. The valve only controls fluid flow during high decelerations brake stops."
Here's how to test the combination valve, according to the factory procedure. You need to have the brake warning light switch hooked up or at least check the switch's continuity in the different modes, using an ohmmeter...You may be able to use the OEM CJ-7 brake warning light for this function. That would preserve the light's function:
Pressure Differential Switch—(1) Have helper sit in driver's seat to apply brake pedal and observe red brake warning light. (2) Raise vehicle on hoist. (3) Connect bleed hose to a rear wheel cylinder and immerse hose end in container partially filled with brake fluid. (4) Have helper press and hold brake pedal to floor and observe warning light.
Results:
1) If warning light illuminates, switch is operating correctly.
2) If light fails to illuminate, check circuit fuse, bulb, and wiring. The parking brake switch can be used to aid in identifying whether or not the brake light bulb and fuse is functional. Repair or replace parts as necessary and test differential pressure switch operation again. Note: If warning light still does not illuminate, the switch is faulty. Replace combination valve assembly, bleed brake system and verify proper switch and valve operation.Now you can bleed the combination valve and brakes. Start with your current brake system (Rubicon combination valve installed with OEM CJ-7 master cylinder). Make sure the combination valve aligns in the stock '05 Rubicon way, with the front and rear lines attached in their correct positions. Here's the factory procedure for manual bleeding and pressure bleeding, beginning with manual bleeding:
Use Mopar brake fluid, or an equivalent quality fluid meeting SAE J1703-F and DOT 3 standards only. Use fresh, clean fluid from a sealed container at all times. (1) Remove reservoir filler caps and fill reservoir. (2) If calipers or wheel cylinders were overhauled, open all caliper and wheel cylinder bleed screws. Then close each bleed screw as fluid starts to drip from it. Top off master cylinder reservoir once more before proceeding. (3) Attach one end of bleed hose to bleed screw and insert opposite end in glass container partially filled with [clean and fresh] brake fluid. Be sure end of bleed hose is immersed in [clean] fluid. (4) Open up bleeder, then have a helper press down the brake pedal. Once the pedal is down close the bleeder. Repeat bleeding until fluid stream is clear and free of bubbles. Then move to the next wheel.
Pressure bleeding procedure:
Use Mopar brake fluid or an equivalent quality fluid meeting SAE J1703-F and DOT 3 standards only. Use fresh, clean fluid from a sealed container at all times. Follow the manufacturer's instructions carefully when using pressure equipment. Do not exceed the tank manufacturer's pressure recommendations. Generally, a tank pressure of 15-20 psi is sufficient for bleeding. Fill the bleeder tank with recommended fluid and purge air from the tank lines before bleeding. Do not pressure bleed without a proper master cylinder adapter. The wrong adapter can lead to leakage, or drawing air back into the system. Use adapter provided with the equipment or Adapter 6921.
As for bleeding, I suggest that you vacuum bleed the system if the combination valve will tolerate that kind of bleeding while remaining in a centered mode. I've used a compressed air actuated vacuum brake bleeder for years and believe this is the safest way to bleed brakes: fast, thorough and intended to completely evacuate debris and old fluid. Most often, one person can easily bleed the system.
Envision pressure or manual bleeding: Either of these methods allows debris to remain near the wheel cylinder sealing cups or caliper piston edges while fluid under pressure exits from the centrally located bleeder valve. By contrast, a vacuum bleeder at a wheel cylinder or caliper does exactly the opposite: It draws the debris and old fluid out of each wheel cylinder or caliper!Note: I use a vacuum bleeder to complete purge my brake systems of old fluid—periodically. This extends rubber seal life, reduces risk of corrosion damage and improves braking performance...If there's interest, I'll start a new topic post on this subject...
You now have information on the combination valve's functions and how to troubleshoot the valve. Bleed the system properly, and see if that provides normal apply pressure at each wheel's brakes...If the rear brakes still fall short and do not have adequate pressure at the calipers, you need a four-wheel disc master cylinder.There are pinpoint diagnostic tools for brake pressure troubleshooting. A four-wheel brake pressure testing kit can read actual brake apply pressure at each wheel. Dealerships, brake shops and high performance automotive shops can often perform these tests. This tool can pinpoint the hydraulic system trouble we're addressing here...I have a brake pressure testing kit and will share details at the "Diagnostic and Specialty Tools & Equipment" forum.
If you have further questions, post a reply!
Moses -
You should have a Dana 35 rear axle with 7.625” ring gear diameter, adequate for the four-cylinder, also used with the 4.0L six in YJ models. The 35 axle will work to 33” diameter tires.
The 35 has an oval diff cover, the 44 cover has flat left and right sides. I've placed diff cover photos below of a Jeep Dana 30 high pinion front, a Dana 35 and a Dana 44 rear:
At left is a Dana 30 front axle, high pinion like a stock YJ Wrangler. Center is a Dana 35 rear in a YJ Wrangler. Right is a Dana 44 rear in a later TJ Wrangler. Note cover shapes. (Click to enlarge.)
Cannot open these photos? Consider joining the forums—for free—to get full access!
I did a step-by-step article at the magazine on rebuilding a Dana 30, similar in basic ways to both the 44 and 35. For understanding concepts like the carrier bearing preload, ring-and-pinion gear backlash and pinion depth measurement, you'll find the article useful. Read the article before you take the plunge. If you have a factory-level workshop manual, use it and follow the step-by-step procedure. My article is at http://www.4wdmechanix.com/How-to-Dana-30-Axle-Rebuild.html.
Primary difference between the 30, earlier 44 and the Dana 35 is the Dana 35’s use of a crush sleeve for pinion bearing preload. The 30 and earlier 44 typically use a shim stack...Use care when adjusting the pinion bearing preload, as over-tightening requires removal of the new crush sleeve and installing another one—the bearings need their slight preload, and over-tightening the pinion load will crush the sleeve too much.
Simply backing off the pinion bearing nut to reduce load (a common mistake) will loosen pressure from the crushed sleeve. In this case, the pinion relies totally on the pinion nut for holding preload…The nut is unsafe, as the bearings are not loaded from the backside.
If you’re on a budget or time constraints, we can discuss servicing the differential without removing the pinion nut, leaving the pinion shaft in place. If the axle is otherwise in good condition, this can be done.
Also use care when removing the differential “gear shaft lock screw” and the shaft. The screw and shaft removal is necessary to access the axle shaft C-clips and remove the axle shafts (necessary step for differential removal). Factory level manuals like to trivialize this step, showing a simple box end wrench for loosening this screw. The screw is high tensile and susceptible to snapping while being removed, especially after a lengthy time in service.
I actually prefer using an air impact, set to very light pressure, for “jolting” this screw loose. The stretching force of a socket and hand ratchet, or fiddling with a box-ended wrench that can round off screw head corners, is not a good idea. “Twisting” this stubborn screw out with hand tools often results in the screw suddenly shearing.
A sheared gear shaft lock screw is an absolute nightmare. The screw acts as hard as a carbide drill bit if you attempt to drill for a screw extractor. Suffice to say, if you find yourself in this dilemma, I can first offer sympathy and then a practical solution or two! You cannot disassemble the axle without removing this differential gear shaft.
Trust this helps...Will add info as needed!
Moses
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I've shared Sonnax upgrades for the Chrysler RE (Dodge Ram) and RH (Jeep Wrangler) automatic transmissions at the magazine. These are fundamental, in-chassis modifications designed to help any RWD Chrysler A727 or 904/999—and the RE/RH four-speed overdrive units—simply survive.
These Sonnax upgrades are not "high performance" modifications intended for high horsepower pullers or those toting a 9-horse trailer day in and day out. I'm separating needs here. For building a "bulletproof" transmission, there is a whole industry targeting the "performance" buildups of the 47RE and 48RE automatics. We'll make that another topic, for sure!
The basic survival needs are mostly valve body related plus an upgrade band accumulator/apply piston. Accessible in the chassis, you can read about the reasons for these improvements at my illustrated, in-depth article: http://www.4wdmechanix.com/Survival-Upgrades-for-Jeep-and-Dodge-Ram-Automatic-Transmissions.html. I could have replaced the band strut at the same time, which is also an in-chassis change.
This is our 48RE with oil pan removed. I'm about to remove the valve body and accumulator piston for Sonnax upgrades. See the heavily illustrated article for details.
(If you can't see these photos, join us as a member—for free—and get full viewing privileges!)
I am curious about the 48RE transmission's cooling needs. Our Cummins diesel application has an OEM external cooler with a thermostat, and aftermarket coolers, at least the "universal" ones I've seen, do not have this provision. Is there a cooler system for these transmissions that incorporates a thermostat, or is the thermostat really necessary?
The magazine's 2005 Ram 3500 operates from a four-season, high desert climate (4400 feet elevation). Winter can be sub-zero F at the extremes. (Summer is hot, it will be 104 degrees F this week.) Without the thermostat on the cooler, is there a problem?
What capacity cooler will actually replace the OEM and improve the system? Who makes the best retrofit coolers for these truck automatic transmissions? Any "direct replacement" types, or do they all require custom fit and mounting brackets?
We do plan to tow, and the truck weighs plenty empty: 9,100-plus pounds. Would like to keep the 48RE alive...We don't abuse it, but we do use it!
Moses
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If the steering gear kit does not talk about retrofitting a pump, I'll guess that the OEM pump can work. If an issue does arise and the '09 pump is a direct replacement, that's worth exploring.
Curious about the Fleece coolant bypass and why? Double stack transmission cooling sounds ample...I have some questions and will start a new topic on the 48RE and cooling. See that post...Thanks!
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Well stated and factual, Tim!...Thanks much for jumping into the discussion, Rich will benefit from your excellent points!
I'm partial to the WJ for all the same reasons, and the 4.7L V-8 has much better fitment in the chassis. The 4.0L inline six also does an admirable job, the body styling is contemporary. Find a good one and enjoy the last front and rear beam axle Grand Cherokee. The WJ Grand Cherokee is the "last of the fundamental 4x4" SUVs...Expect WJs to see more trail time as the price of access continues to drop for these 1999-2004 models.
This week, I posted glowingly about wife Donna's all time favorite FSJ, the Grand Wagoneer...A V-8 Jeep WJ Grand Cherokee would be the closest contemporary ride quality, performance and stable "feel"...The WJ lives up to the "Grand" moniker better than any other Jeep SUV built since 1992. Donna would enjoy driving one—and I'd like it, too!
Moses
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Thanks for catching this post...It's among my favorite subjects, as you might have guessed...
Once the axle gearing is correct, the other factors that drop fuel mileage on your '06 Ram 3500 Cummins would be 1) the increased vehicle height (kiss off aerodynamics of any kind!) and 2) the vehicle's weight over stock. I wound up in a similar situation with a 4" lift, 35" tires and a carload of "cool" accessories! Not sure of your accessories, I added approximately 1,350 pounds to my over-the-road, "unloaded" weight...kind of like perpetually pulling a well equipped tent trailer!
Hey, we all like the "look" and utility of a lifted and accessorized Ram 3500 4x4! Here, the truck we purchased new in October 2004 is undergoing a metamorphosis in 2011, getting ready for show time at the BFGoodrich Tires booth, Off-Road Expo at Pomona, CA! Let's see now, the lift, wheels and 35" tires, we'll add a utility fuel tank that takes us to Moab, Utah and back from the Reno, Nevada area...and that M12000 Warn winch will be a dandy when needed! Oops, there went the 25 mpg. Time for a 4.56:1 axle gear change out!
(Can't see the photos? Join our free forums and get the full benefits of membership!)
Most have no idea how quickly the upgrades and accessory weight add up: Try oversized American Eagle wheels and BFG tires for at least 150# over stock including the spare; a Mopar lift kit after swapping out OEM parts for an added 50 pounds; a Warn M12000 winch for 140# (bare winch wound with wire rope); front and rear HD bumpers for an extra 300#; a Transfer Flow cross bed fuel tank with additional fuel on board: 75 gallons @ 7.1 lb/gallon for Low Sulphur diesel = 532.5 pounds when full plus the aluminized steel tank's weight! Oh, and I do like the three Bestop Treksteps for 60 pounds plus.
I'll comment on your gearing projections, just did the math...If your tire's revolutions per mile are around 560 (Toyo rating for several popular 37" diameter tires, confirm your exact revs per mile), then here are your engine speeds at practical road speeds in overdrive (0.69:1):
4.88 gears @ 70 mph = 2200 engine rpm
4.88 gears @ 65 mph = 2043 engine rpm
4.88 gears @ 55 mph = 1728 engine rpm
4.56 gears @ 70 mph = 2056 engine rpm
4.56 gears @ 65 mph = 1909 engine rpm
4.56 gears @ 55 mph = 1615 engine rpm
According to Cummins, you should use the 4.88:1 gears for a truck under 10000# GVWR and intended for 70 mph cruise. In my experience, though, if fuel mileage were your sole aim without carrying cargo or trailer pulling, I would suggest the 4.56 gearing. This would keep you "in the window" for maximum fuel economy. However, even a light travel trailer would immediately tip the scale toward taxing the engine, which could impact both fuel efficiency and engine life—plus overload the transmission (clutch if manual) and driveline.
Actually, with your 37" tires, the 4.56:1 ratio would be much like your 3.73:1 gears with the Ram 3500's stock tire size. (That was also before accessory add-ons and the lift, too!) In overdrive, that off-the-showroom floor truck fell well below Cummins' recommended 2,150 rpm at 65 mph baseline for fuel efficiency and commercial hauling. I'd again emphasize that 23-25 mpg highway was readily achievable with the stock tires, 3.73 gearing and no load at 65-69 mph (approximately 1800-1950 rpm).
If you pull a trailer very seldom and your add-on accessories weight is modest, fuel efficiency would be good between 55 and 70 mph with 4.56:1 gearing and 37" tires. If the add-ons are like mine, however, your truck has a load before you stack on cargo! The 4.56:1 gearing would not be low enough, you'd be better off with the 4.88:1 gears.
Note: This is why I opted for 4.56:1 with the 35" tires, rather than fiddle with 4.10:1, which would have been the direct correction for the bigger tires. We plan to pull a trailer on occasion—without destroying the powertrain. Also, as I've shared, between the lift height and added accessories weight, this is not the stock truck any more.
Your decision comes down to load and intended cruising speed. Considering the height and weight of your Ram 3500 Mega Cab, you'd likely be "happier", performance wise, with 4.88 gears. When you want fuel efficiency, hold the speed to 65 mph. If that's too slow and you want to "cruise" at 70-plus mph yet get the best fuel efficiency for that rate of speed, consider 4.56:1 axle gearing. You can see by the calculations that the engine would be in Cummins' recommended zone of 2100-2400 rpm when cruising at 72 mph (2114 engine rpm) with 4.56:1 gears in overdrive. With 4.88:1 gears at 72 mph in overdrive, the engine would spin 2263 rpm and eat up fuel.
Cruise speeds above 65 mph will eat fuel, regardless...Moving as much mass as our trucks at speeds above 65 mph requires increasingly more fuel. Base your choice on what cruise speed you find acceptable on the highway—the faster you go, the more fuel the engine will use...guaranteed!
The acceleration might be marginally better with 4.88:1 gears. In terms of gear stamina with a given ring gear size (11.5" and 9.25" in our case), the 4.56 gears are actually stronger due to the larger pinion gear head size. (This is slightly offset by the 4.88:1 additional gear reduction, which helps reduce load a bit.) Given our Ram 3500 ring gear sizes, the stamina distinction is not as severe—nothing like sticking 4.88:1 gears in a Dana 35 Jeep rear axle with a 7.625" diameter ring gear!
We can kick this around more, Megatron. Cummins recommends spinning the engine for "efficiency" and, at least commercially, does not want to "lug" the engine below 1900 rpm at highway cruising speeds. Note that a truck under 10000# GVWR with an H.O. 5.9L Cummins ISB engine is less susceptible to lugging than a Cummins ISB engine in a medium-duty truck.
If you're running an aftermarket performance module or "chip", or have done any other tuning or engine modifications, we need to discuss those variables, too...That could change the rpm scale for maximum performance and fuel efficiency, in turn shifting the rpm band for the gearing.
Moses
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Nice analogy for the BD Performance sector support bearing: ranch grade, and that's good! Wondered about your shimming of the plate in the photos, thanks for the explanation. Others would want to position/match the bearing plate for whatever "height" or alignment their pitman and steering gear present. This likely applies to any gearbox upgrade (other than Redhead, they work with the OEM gear). A Borgeson or Mopar upgrade steering gear (with or without an aftermarket dropped pitman arm) could, like you describe, put the sector and nut at a different point than stock, enough to require relocating the BD Performance bearing brace.
Not surprising that you should mention the pump. I did talk to Jeff Grantmeyer at Borgeson about their upgrade steering gear and the stock pump. He said the stock pump seems to be Ford-type and could be marginal in output. We can research and compare output volume and pressure; however, the wild card is the specs for the upgrade Mopar steering gear.
I have the "factory" shop data from our Ram truck era, but any upgrade, retrofit gear might follow another guideline. The Mopar upgrade gear might use the same specs as the '09-up stock steering gear/pump requirements. I'm willing to research this further if you think there's an issue with your pump output. If the '09-up pump is the fix, we need to verify the pump mounting for the 6.7L Cummins diesel, too.
I'm guessing that your Mopar upgrade steering gear kit did not mention the pump and whether to test capacity or pressure? They do not describe a need to change the pump, right?
I'm sure you like the Cummins diesel, much room for discussion here! I offer some basic upgrades for every Chrysler RE/RH automatic at the magazine. The Sonnax valve body work is a bare minimum: http://www.4wdmechanix.com/Survival-Upgrades-for-Jeep-and-Dodge-Ram-Automatic-Transmissions.html. With your '06 Ram 3500, I'm guessing you've gone deeper, Megatron!
I am curious if you changed or added a transmission cooler, and if so, please start a new topic on that one. I'm at a crossroad with our '05 Ram 3500. After doing the valve body gains with the Sonnax upgrades, I now need to increase cooler flow capacity. Not sure whether the factory "thermostat" in the OEM cooler is essential, I have a restriction issue and would like to replace the OEM cooler. Note: Sonnax recommends removal of the anti-drain back valve after installing the valve body upgrades. I do not recommend removing the anti-drain back valve for any other reason! My article clarifies these issues.
Moses
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This is great info...I like your approach! The new photo sizing is perfect...Mopar's replacement gear is just what I want!
Thanks for clarifying the need for a new dropped pitman arm with the Mopar upgrade gear, I sensed that was the case from our earliest discussion. Pleased that the new gear box is that much of an improvement.
The BD Performance brace looks well conceived. Does the bearing plate have a replaceable, permanently sealed bearing? Should last a long time in this kind of service.
I, too, sacrificed my factory (right side) damper end bracket during the lift kit install. (See my photos in the earlier threads at this topic, I fabricated left and right side, weld-on brackets from the supplied "bolt-on" pieces.) So, I'll be fabricating a damper solution, too, based on the layout of the new steering linkage: '09-up factory Y-type with a dropped pitman arm or possibly the Pure Performance linkage alternative. The Pure Performance linkage would work with the stock replacement pitman arm that Mopar supplies with the upgrade steering gear kit; however, it gets into a mix of Mopar and Ford Super Duty tie-rod ends. Will investigate here...
Engineering, fabricating and welding come together on your four-link upgrade. I've offered a welding section at the magazine and will take that discussion to the welding and metallurgy forum. Weld Mold Company has great niche filler materials for welding alloys if you need them. We can move to the welding category to expand on that subject...
Sounds like the dealer recall was looking for either stock replacement Mopar tie-rod ends or your original lift kit pitman arm. Fabtech or Superlift, each had a Ram truck recall that involved Mopar, apparently. (Was your truck sold originally with a dealer-installed lift?) I like your priorities in any case: family safety!
Your '06 looks great, Megatron, thanks for sharing the photo! Of course, I'm partial as the owner of an '05 Ram 3500 bought new. Each of us has a "keeper", we're in it for the long haul! (Priced a new one lately? That's an incentive to keep ours!)
Do you have a Cummins? 48RE automatic or 5600 manual transmission?
Moses
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Some of us are old enough to remember the "Datsun" 520, 620 and 720 pickups. During my University of Oregon years in the late 'seventies (graduated in 1980), I recall the rugged mini-Datsun pickups all over the Pacific Northwest. Nissan Frontier and Titan pickup owners might find the name strange, but Nissan kept the Datsun moniker on U.S. models into the first 4x4 mini-pickup years.
The first Nissan-Datsun 4x4s were a groundbreaking design. Toyota had built its first 4x4 mini-truck around a scaled down Land Cruiser layout, with live beam axles front and rear. This was 1979, and Nissan faced a choice: Use beam front and rear axles, like a scaled down Nissan Patrol approach, or do IFS at the front with half shafts.
Ford launched its Twin-Traction Beam front suspension in 1980, and it's not surprising that Nissan opted for an IFS. The design was unique but not to Nissan. Datsun Z-cars had used an IRS drive axle for years, and this could be flipped over and put at the front of the Datsun 4x4 pickups, adding steerable knuckles.
IFS was advanced but did not stand alone for long. By 1983, G.M. S/T 4x4 trucks sported IFS front driving axles, and the trend continued. While the Toyota mini-pickup became the iconic 4x4, there are many early Datsun 720 4x4s still active...
Datsun 4x4, Nissan Hard Body, Titan and Frontier pickup owners are encouraged to share their experiences, technical questions and upgrades—right here at this forum. Join us, we'd enjoy hearing from early Datsun IFS 4x4 truck owners. After all, you're part of the growing Nissan legacy!
Moses
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The Grand Cherokee ZJ and WJ were each “upscale” with more accessories and even V-8 options. A 'Grand is slightly longer wheelbase and weighs more than an XJ Cherokee. This makes the base 4.0L inline six engine less attractive in the ZJ or WJ, as it works harder than in an XJ.
Through the WJ Grand Cherokee, the model has a uni-frame body and beam axles front and rear like the XJ Cherokee. The beam axles are a big plus for both longevity and service needs. Rear axles can be a Dana 30 or a 44 (aluminum center section) on the V-8 models.
If I were considering a Grand Cherokee, my preference is the 1999-2004 WJ model. That said, repairs and parts can be more expensive for the Grand Cherokee than an XJ Cherokee, and there’s typically more to go wrong at higher mileage.
A used, higher mileage Nissan Pathfinder could eat you out of house and home—very expensive parts and service, definitely a challenge to work on yourself…Compared to the fundamental design of an XJ Cherokee 4x4, a V-6 Pathfinder with high mileage would be more like a European car—something to avoid at high mileage.
The XJ Cherokee, it turns out, is the most utilitarian 4x4 SUV ever built—for functionality, reliability and from a maintenance or repair point of view...This is the "Volkswagen Beetle" (air-cooled era) myth come to life: The XJ Cherokee will actually run 250K-300K miles if maintained properly.
By contrast, an air-cooled Bug was lucky to see 100K miles without new cylinders, head and valve work plus lower end engine bearings—not to mention chronic replacement of chassis-length wire control cables, a Solex carburetor that would drop its discharge tube down the carb throat and take out valves and a piston, or the braided fuel hoses that baked under the rear deck until they split and spewed fuel onto a scorching hot, "fan cooled" engine with an oil cooler—and set the car on fire.
Need I say more? (I could describe the VW Type II bus and Type III hatchback and fastback frailties.) Better we should be happy that AMC/Jeep designed and produced the XJ Cherokee 4x4 compact SUV.
Moses
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Haven't seen the article, so I'm unaware of the "why". Shooting from the hip, here's my take: We have a ’99, and it’s the best 4.0L engine, PCM, overall package. Later have coil-on-plug ignition and a less desirable cylinder head, earlier '96 and '97 have transition from OBD to OBD II electronics. ’91-’94 would be acceptable, some 4.0L sixes in this era have piston noise issues (typically when cold) from block core shift, not necessarily a reliability issue, more a nuisance…’87-’90 is the Renix EFI/MPI, older technology and a less efficient cylinder head, not terrible, just a totally different troubleshooting and diagnostics approach that makes the '91-up Chrysler MPI/EFI system attractive. Of course, for home diagnostics, OBD II is superior and more accessible to an inexpensive code reader or scan tool.
’96 takes the hit for transition from OBD to OBD II issues in the electrical and electronic circuits, some carry to '97. If you notice, there is no "1996" YJ Wrangler, and the first TJ (1997) bursts on the scene with OBD II circuits incorporated. XJ Cherokee sales projections for 1996 were too strong to skip a model year, so haphazard OBD II wiring, electronics and an OBD II type PCM strategy went into place on this model.
Though they do not list '84-'86 XJ Cherokee models (as most won't), these vehicles are okay with the 2.5L four (if you like four-cylinder power), better yet the 1986-90 2.5L four with TBI. If stuck with a 2.8L V-6, consider a G.M. 3.4L bolt-in V-6 crate motor replacement that eliminates the weak small journal crankshaft, rear main seal leaks and other quirks with the early design 2.8L V-6.
As an historical point of interest, AMC got stuck with this early version 2.8L V-6 engine through 1986, even though G.M. vehicles went to a better/bigger journal crankshaft and rear main design in the 1985 2.8L V-6. If the 3.4L V-6 crate engine is still in the G.M. parts inventory, listed as a direct replacement for the 2.8L V-6, you can get respectable performance and have a carbureted V-6 that actually works. I would expect to pay a song for any '84-'87 XJ Cherokee, the only incentive for buying one.
I’d say the Jp assessment is reasonable. There are quirks with any of the XJ Cherokee model year groups, and items like the vacuum disconnect front axle come to mind for earlier years—the ’98-’99 might have the least foibles. Overall, the XJ Cherokee offers an inexpensive price of admission and often matches the Toyota 300K Mile Club for reliability and longevity. I might add that it's much easier to service and restore an XJ Cherokee than any Toyota truck in that year range!
Moses
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As a point of interest, I looked up the popular recalls for our Ram 3500 trucks, Megatron...Your recall might have been related to the Fabtech or Super Lift pitman arms. Or maybe you caught the tie-rod end recall that I received. (This is for later models or any '03-up that had a tie-rod end changed using Mopar parts.)
In any case, these are the two recalls posted, nothing specific to the steering gearbox yet: http://www.motortrend.com/cars/2006/dodge/ram_3500/recalls/.
Did your recall fall under the steering box itself or these other two items? The dealer would have avoided a repair on the pitman arm, as you use the Carli item. You might compare your 2010 steering linkage to the tie-rod end recall. Make sure your T-linkage has the safe tie-rod ends and not the tie-rod ends that Mopar recalled...
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While many see modern Land Rovers as eccentric tractability for the world's gentry, one model is a clear exception: the Defender 90. Land Rover's legacy of rugged, military grade 4x4s comes together in this iconic and sought after model.
Bill Burke of 4-Wheeling America has been a personal friend for many years now. We co-instructed 'Tread Lightly' 4WD Clinics across the U.S. years ago, and Bill is a Camel Trophy veteran...I competed in the CliffsNotes version, the Land Rover Trek competition, which did a much abbreviated (all in one long day) facsimile, using Land Rover Discovery models.
Bill has been a Defender 90 aficionado ever since his Camel Trophy experience. A closer look at this model reveals why. When he purchased his Land Rover Defender 90, Bill was in his element! He has carefully maintained and upgraded this 4x4 to meet every need in his four-wheeling instructional and guiding service.
I've driven the popular, shorter wheelbase off road 4x4s built since 1941 and have owned or officially tested more than my share. The short list for optimal 'wheeling would be Jeep CJs, Wranglers, the Land Cruisers, Nissan Patrol, Ford Bronco, I-H Scout and Scout II and the Defender 90. I single out these vehicles because benchmark, tight access routes like the Rubicon Trail have very specific requirements.
I have a quick formula for vehicles well suited for tight, twisting 4x4 trails. Since most popular 4x4s can now be chassis "lifted" and equipped with oversized tires, it comes down to useful wheelbase lengths.
In my view, the best 4x4s for Rubicon Trail travel have a wheelbase no longer than 104". I use this arbitrary length to include the vintage Jeep CJ-6, CJ-8 Scrambler or an XJ Cherokee in modified form. A short wheelbase improves break-over angle. Good approach and departure angles make the best trail runners...
Note: Some might ask why I don't stretch that figure to the 116" JK Wrangler Unlimited's wheelbase length. That Jeep needs 37" diameter (significantly oversized!) tires to successfully negotiate the rougher sections of the Rubicon Trail without damage.
The Land Rover Defender 90 has a 92.9" wheelbase, Toyota FJ40 Land Cruiser has a 90" wheelbase, and the original Ford Bronco is a 92" wheelbase. Track widths are similar, and all three of these vehicles have excellent approach and departure angles—as do Jeep CJs and Wranglers.
Narrower dimensions of traditional, short wheelbase Jeep utility 4x4s excel on ultra-tight access trails. The JK Wrangler is the wider, longer exception, these features intended for better vehicle control on-highway and, overall, a lower center of gravity to reduce rollover risk.
I have owned two FJ40s and would characterize them as among the very best off-pavement 4x4s ever. The wider track width lends center-of-gravity stability, the shorter wheelbase provides tight back country access—yet still offers reasonable on-highway handling for a 4x4 designed for primitive country.
To prove this point, I once towed a 21-foot travel trailer across the Mojave Desert in a wind storm. That FJ40 OFF-ROAD Magazine project had a 383 Chevy V-8 stroker motor conversion, and I used a load distribution/equalizer hitch with a sway control brake (neither item out of the ordinary for safe towing). The vehicle was rock steady. A Defender 90 or early (1966-77) Ford Bronco can be set up to accomplish the same.
More details about the Defender 90 and its predecessors: http://en.wikipedia.org/wiki/Land_Rover_Defender_90#Land_Rover_Ninety_.26_One_Ten
Simply on dimensions alone, the Defender 90 scores well. Add to that a separate ladder frame with beam front and rear axles, refined and tuned suspension, and the Defender 90 ranks up there. Overseas, the turbo-diesel powered Defender was hugely successful. In the U.S. market, which only lasted from 1993-97, the proven aluminum 3.9L and 4.0L V-8 worked well. I know this engine from its roots, the 'sixties Buick/Olds 215 aluminum V-8. We can discuss that history if you'd like!
I'd value opinions from Defender 90 owners and seekers. Join this forum and let the discussion begin!
Moses
EFI Fuel Filter Upgrade And Other Fixes
in 1972-86 AMC/Jeep® CJ and Jeepster Models
Posted
Well, if it simplifies the install and hose matching, there's likely no harm in doing a 3/8" fitting on the pick up side. If you run 3/8", I do want your feedback on this, including pump heat in service.
One way to take the "mystery" and second guessing out of this issue is to measure amperage draw at the pump while it's operating—using 5/16" versus 3/8" pick up hoses. This is a more scientific approach and would indicate the load on the pump. If there's a "restriction", as you suggest, with the use of a 5/16" hose and fitting, that will show up in higher amperage draw. The measuring device needs to read 1/10ths of an amp or smaller.
To be clear, the rating on the pump should be with the furnished or intended fittings installed. Unless vendors are substituting smaller (5/16" versus 3/8" hose size) fittings—with the pump's flow rating based on the bigger fitting—there's little risk of "starving" the engine for fuel. If you have suspicions about the pump's intended input/output fuel fitting sizes, research the manufacturer's ratings and the fitting sizes recommended.
Volume is an even smaller concern. We know the pump pressure and GPH flow rate. Based on that, if the rating is with the 5/16" fitting, it would be a moot point which fuel hose size you use. The 4.6L inline six cannot burn more fuel than what we understand to be the flow ratings for your pumps.
As for 3/8" versus 5/16" hose flow rate, most concerns are on the pressure side, not the pick up side. Here's a link that has considerable research information on pressure drop and its relationship to distance: http://www.dultmeier.com/literature/fluid-flow.asp. You might want to wade through this material, it does address hose sizing, too.
Note: Do take distance into account when sizing hose. If you plan to run hose for a long distance on the pressure side, consider the larger size hose. Also consider hose length when sizing the pick up side.
From a strictly practical standpoint, the use of 3/8" hose was popular on multiple carbureted engines in the muscle car era. I've seen little use of that size hose for fuel supply on other production engine applications. For peace of mind, take a moment to measure the OEM steel fuel pipes furnished with your Mopar EFI kit, the supply and return pipes that connect at the rail end.
Another consideration that you did not detail is the inside diameter of the furnished fuel pump fittings. If these fittings are barbed or step nipples, I would be concerned about the I.D. of the fitting. If the fittings are standard fuel type (clamp style) for 5/16" or 3/8" hose, then you should not have a restriction. Hose size and flow volume take fittings into account: You can't have a hose installation without a fitting! If the fitting I.D. is small, like a barbed fitting, I would step up the hose size to 3/8" and use the correct fitting for that size hose.
Better yet, you have fuel flow under scrutiny by continually monitoring the fuel pressure at the EFI fuel rail. If you see fluctuations in the pressure, especially with a new regulator, you can suspect the fuel flow volume to the rail. Volume reflects pressure and flow rate, so each will be apparent in the pressure reading at your shiny new fuel pressure gauge on the dash!
Can't wait to see that fuel pressure gauge in service...What an onboard diagnostic tool!
Moses