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Moses, thanks so much for responding.  I’ve actually been following many of your posts and articles regarding tuning up the 2.5 TBI.  I will check these posts you’ve listed and see where to go from there and provide feedback to this post.

Regarding the 2nd issue (Loud sound) I’m really hoping that it’s what you say such as the driveshafts/splines and NOT my renewed motor or Tranny.  The motor still goes on and sounds very smooth and the transmission changes gears smooth also.  It makes sense that it is a driveshaft sound and how it Rocks the Jeep. 

For the first time in 27 years while driving it “kicked” and made a loud metallic sound and I felt as if I ran over some huge hole or rock.  I could not tell if the sound came from the motor or transmission.  But it jerked enough that my radio popped out of place.  I stopped to check but there was no hole or rock.  Everything under the Jeep was OK – no leaks, dents or missing axles.  I really thought something fell off.   But the Jeep kept going and the transmission changed fine and 4 minutes later it did again.

Background – the motor was recently rebuilt because there was noise from bad piston rods and a bad blow-by problem.  The rebuild was pretty good and the motor goes on nicely and idles at about 950RPM.  I would really like to cure issue 1 while issue 2 scares the heck out of me. 

Here are more details on my setup:

All driveshafts are original and there is no lift kit.  But my tires are huge! I got them cheap and used along with the rims from a fellow worker.  I thought they would look great but I also read that it takes a lot more work for the 2.5 Jeep to move them so I can’t go 5th gear unless it’s a pretty leveled highway.  Up hill its mostly 3rd or 2nd gear now.

  1.               Tire specs are 33 x 12.50 R15 (even though using a tape measure I get under 31” high).
  2.             I lifted by adding 1.25” shackles and a mechanic who is good at bending leaf springs added 2” by bending the factory leaf springs. Only the rear springs.  
  3.                The rear drive-line length is 18.25” from transfer case to U-bolt and the Angle is about 23°.  Is that clear info or do I need to measure differently?

Other than that, there are no other modifications to chassis or driveshafts.  I don’t think the front driveshaft may have made the noise since I wasn’t in 4x4.  Is it still possible? 

Other things I will be checking are  transfer and Axle fluids.  I did have a front passenger side fluid leak.

I’ve attached a picture of the tire.  Thanks for your help.

 

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Hi, Sabueso...Here are some quick notes on your rear driveshaft and spring modifications:

6 hours ago, Sabueso said:

All driveshafts are original and there is no lift kit.  But my tires are huge! I got them cheap and used along with the rims from a fellow worker.  I thought they would look great but I also read that it takes a lot more work for the 2.5 Jeep to move them so I can’t go 5th gear unless it’s a pretty leveled highway.  Up hill its mostly 3rd or 2nd gear now.

Gearing is a problem on the 2.5L four-cylinder Jeep Wranglers.  They should come stock with 4.10s (1990 might be 3.73s), but that's barely tall enough for a stock 29"-30" tire diameter.  33" needs minimum 4.56s, some drop to 4.88s.  The TBI engine produces better bottom end, in my experience, than the later MPI 2.5L, which is a definite shift to 4th gear on any kind of grade with the AX5 manual transmission.

  1.               Tire specs are 33 x 12.50 R15 (even though using a tape measure I get under 31” high).

    These tires should measure close to 33" with the tires and wheels off the vehicle.  Radial tires flatten more on their bottoms when loaded than old bias-ply tires; this lowers the measured height from the ground to the top of the tires.

  2.             I lifted by adding 1.25” shackles and a mechanic who is good at bending leaf springs added 2” by bending the factory leaf springs. Only the rear springs.  
  3.                The rear drive-line length is 18.25” from transfer case to U-bolt and the Angle is about 23°.  Is that clear info or do I need to measure differently?

      You're on the right track with the driveshaft questions.  For one thing, the shaft looks too short, likely due to a stock shaft with a 3.25" overall chassis lift.  This kind of lift on a YJ Wrangler normally would include a dropped skid plate kit (1"-2" maximum) and re-aligning the U-joints.  A dropped skid plate typically requires rotating the pinion upward.  This matches/cancels the rear U-joint angles and at the same time shortens the distance between the transfer case and the rear pinion flange.  At over 3" lift, you're on the cusp for a new CV rear driveshaft conversion with a Slip Yoke Eliminator kit.  See the recent exchange at: 

        You might be able to get by with the stock driveshaft after a skid plate drop and rotating the pinion.  However, make sure the two rear shaft U-joints cancel angles, do not attempt to shorten the gap with too much pinion rotation...At this point, your rear driveshaft looks too short, the slip yoke reveals a lot of exposure with the vehicle on the ground at curb height and weight.  It's possible that the driveshaft gap stretched even further from either the chassis rising or a wheel dropping into a pothole.

      If you're curious about the actual driveshaft engagement at full drop, lift the vehicle by the frame and set safe stands under the frame rails (or lift the vehicle on a hoist).  Let the rear axle droop with the tires off the ground.  I believe you'll be surprised at the minimal spline engagement at the slip yoke.  This should provide a clue.  You will also see spline damage if the slip yoke actually disengaged from the transfer case output shaft, and if the rear shaft comes loose and hits the ground, you have a very dangerous situation and possible loss of vehicle control.

Regarding the front driveshaft, you can have the same issue at the slip coupler.  It's splined, too.  The likelihood of coming loose is much less though, as the front driveshaft is longer than the rear one.  Often with a mild lift, the front driveshaft can be kept.  As for pinion angle changes at the front axle, you are limited by the front axle's caster angle limits.  At the rear axle, the typical approach is hard steel wedges between the axle perches and leaf springs.

More to share:

Quote

Other than that, there are no other modifications to chassis or driveshafts.  I don’t think the front driveshaft may have made the noise since I wasn’t in 4x4.  Is it still possible?

No, the spline coupler and front driveshaft should not spin in 2WD like a TJ Wrangler, you have a front axle disconnect system that prevents the driveshaft from spinning—if the disconnect is working properly.  Which raises another possibility:  You could have a front axle disconnect system that is defective.  This could ratchet the engagement of the right side axle shaft or cause the disconnect to bind up arbitrarily.  Did the steering jerk when you heard the noise?  Could the noise have been from the front axle? 

Other things I will be checking are  transfer and Axle fluids.  I did have a front passenger side fluid leak.

 This fluid leak is in the area of the disconnect system.

Moses

 

 

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Hi Moses,

As always your suggestions are top notch.  Thanks for seperating both topics so that we and the community can concentrate on either one.  Regarding my lift and Loud Bang as you pointed out, my stock Drive shaft is short.  Its gonna take me a while to see what my options are money wise cause these days I'm low on "Hobby Funds".

But I'm soaking in all these tips and I'm going to get to work analyzing the situation. 

First off I'm considering changing the tires to something more manageable by the 2.5 and not so wide.  Maybe 31"s.  Truethfully the amount of dirt/water/mud reaching the cabin is really annoying my wife and that's just from regular roads.  And I'm sure the YJ would run a little better too.  

Checking the skid plate drop I can see its $200 plus $135 shipping since I live in the Caribbean (Puerto Rico).  A new drive shaft or SYE is a little more than that too.  My buddy Jeep Mechanic has a lot of used Jeep parts and maybe he's got some solution for me.  I'm going to study your posts a little more because there are some terms I'm not familiar with such as "spacers" and "rotating the pinion".  I'm gonna need some time to try things and provide more feedback.

Correction:  I remembered my front Drive-shaft is not stock.  I replaced it with a later model and it is longer than the original.  The front is not lifted like the rear springs.  Just the longer Shackles 1.25".  Thanks Moses.

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Sabueso...I understand the cost of parts and shipping.  No "Amazon Prime" to Puerto Rico, I'll keep that in mind with my suggestions...Let's discuss some "cost effective" solutions.

The term "spacers" applies to the inexpensive steel sleeves that get placed between the skid plate and frame.  Longer bolts of correct hardness with locking hardware are also necessary...I think of this as a "band aid" solution, though many aftermarket lift kit suppliers consider the spacers a normal part of doing a minor lift.  The link I shared at the forums has full comments on both the spacers and pinion rotation:

 

"Rotating the pinion" is a term applied to turning the entire axle housing by the use of wedge shims, spring perch relocation or leaf springs with a different arch.  Any of these methods will move or rotate the axle's pinion shaft upward.  Visualize the "pinion" as the pinion shaft.  The shaft has a center line.  Rotating the pinion is really rotating or tilting the center line of the pinion shaft.  Somehow this confusing phrase caught on.  By rotating the pinion shaft, you change the U-joint angle and driveshaft gap.

When an aftermarket rear CV driveshaft is installed with its double Cardan joint at the transfer case end, the rear (single) U-joint angle gets changed to almost straight, not quite though, actually to a rear/pinion U-joint angle of 1.5 to 2.0 degrees or enough to keep the bearings moving in the U-joint bearing caps.  I discuss this further at the link above.

So, the cheapest "fix" in your case would be to 1) lower the chassis height like you share, to the 1.25" shackle lift only, 2) mount smaller diameter tires like the 31" diameter if they will fit, and 3) adjust the rear driveshaft's U-joint angles to cancel each other when the vehicle is on flat ground at its normal static, curb-weight height.

The spring shackle lift actually rotates the pinion angle slightly, and lowering the skid plate slightly might be all you need to get the U-joint angles to cancel each other properly.  Without a CV rear driveline, your stock driveshaft has single-Cardan joints at each end that need to cancel each other's angle.  

Keep in mind the correct driveshaft length as you proceed.  You want the correct (not too long or too short) driveshaft length for the right slip yoke travel.  You also want U-joint angles that cancel each other out with the vehicle weighted (curb height) on flat ground.  Also make sure your front driveshaft is not too long or short after lowering the chassis.

The change to 31" tires will help restore the gearing.  31" tires and 4.10 gears would be acceptable for the 2.5L TBI engine.  You still are a bit "tall", and there is speedometer error to correct (if you want) by installing a new speedometer driven/"pinion" gear at the transfer case.  Your wife will appreciate the lack of mud and easier access in and out of the vehicle!

I'm glad to answer further questions, Sabueso...

Moses

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Sabueso...Inexpensive, decent design with the steel sleeve, hardware should be properly graded.  Daystar is a major supplier of urethane parts for lift kit manufacturers.  Looks like urethane, should hold up, only a 1" lift which is conservative...

Moses

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Ok so just to follow-up on what I've done.

I visited my Jeep guru up in the mountains who's very good with AX5 transissions and Jeep suspension.

He quickly identified where the bang came from due to the drive shaft's severe angle.  We could see a shiny scar or mark on the drive shaft where the U-Bolt nuts hit and made the loud noise.  I'm relieved its not a motor or Tranny issue.

He actually had some shims around and sold me 2 pairs of 2 degree shims.  So 4 degrees total on each rear tire.  I immediately installed them and I could see the angle of the pinion go up.  He also had a skid plate drop kit but I found it too extreme (1.5") and too expensive.  So decided to create my own home made skid drop.  I used 1.25" longer bolts than stock and used big steel nuts as the spacers which were 1" high  ($14 total).  The slip yoke went back in about a 1/2 inch and the angle of the drive shaft looks pretty good.  The Jeep seems to ride a lot better and no banging or vibrations.  I actually cured another noise problem I was getting from my Cat-converter hitting the skid plate :D.

I'll keep the home made skid drop for a while and keep my eye on it in case it gets loose though its pretty sturdy.  I plan to invest in a pro-looking skid drop later on.  The only thing that "feels" different is my Shifter.  Its a little lower than before obviously due to the skid drop.  As long as it doesn't affect the transmission I'll get used to it.

Down the road I will replace those 33" tires with 31s and less width.  I'm  sure it will be perfect after that.

Thanks Moses for all your input.

 

 

 

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Good, Sabueso!  Innovative, quick fix, that surely was your noise...The dropped skid plate does alter the gear shifter location.  Make sure you can get the transmission completely into each gear...

The only thing I would do now is measure and compare the angles of the rear driveshaft's U-joints.  This should be done with the vehicle parked on level ground and normal weight on the tires and axles.  The two rear driveshaft U-joint angles should "cancel" each other.  

If you don't have a professional angle gauge that is made for this task, no problem.  You can use an adjustable protractor and come reasonably close.  I have the professional tools and also an inexpensive plastic Craftsman protractor that is surprisingly accurate!  When I just want a comparison measurement, the Craftsman protractor works well enough.

Here are some details from Spicer:  http://spicerparts.com/anglemaster/measuring-angles

Here are some inexpensive tools that work:  http://www.homedepot.com/p/Johnson-Pitch-and-Angle-Locator-750/100193539?cm_mmc=Shopping|THD|G|0|G-BASE-PLA-D25T-HandTools|&gclid=COnu8ZKBhdICFUi2wAodz2sK7A&gclsrc=aw.ds

 My Craftsman protractor looks like this one and provides plenty of angles for reference:  https://www.zoro.com/empire-protractorangle-finder-2791/i/G4875127/?gclid=CIGrxNqBhdICFRGewAod1BMA5Q&gclsrc=aw.ds

Here's an innovative approach using your cell phone and an app!  Check this out from Tremec:  http://www.superchevy.com/how-to/transmission/1502-how-to-use-tremec-driveline-angle-finder-app/

Once you are making these measurements with the Jeep fully weighted and at its normal ride height, you'll quickly understand what I mean by "cancelling angles".  One end of the driveshaft is the reciprocal of the other.  This is not difficult to understand when you start taking measurements.

Make sure you have the vehicle stopped, engine off, in gear, E-brake set, wheels chocked, etc.  You may need to rotate the rear driveshaft to find a common point to take measurements.  The professional gauges are often magnetic with a bubble level; the gauge hangs straight down from the U-joint's downward facing bearing cap.  

In any case, make sure the vehicle is safely secured when you crawl under it to take measurements.  Let's see whether the joint angles are correct now or at least within an acceptable range.

Moses

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Very bad news today.  first off thanks for the info on the angle instruments and App.  I downloaded the Tremec App and it works pretty good though I didn't play too much with it.  I need to find the correct spots on the drive train to get a good reading.

Now for the Bad news.  I was doing another test run of the Jeep when I received a very loud noise from underneath that shook the Jeep and turned it off.  I was doing about 52mph on the highway so I pulled over.  After checking underneath and seing everything normal I turn it on again.  Turned on OK so a put it in first gear and got another clank when I tried to move but this time it would not move.  My gut was telling me I blew the clutch.  Tried all gears but nothing!  What was strange was that while it was on I could find all my gears by stepping on the clutch.  Hmmm?

So after a friendly tow stopped by and $40 later it was parked in front of the house.  So I tried to move the jeep again and the tow guy asked me to put it in first, leave it on and put the eBrake on.  Low and behold the rear shaft was moving the pinion yoke but no movement from the rear wheels!  :(

So the loud bang was coming from the rear axle all along?  I've never done an Axle repair or rebuild so already I've started to search.  I've got a feeling its not gonna be too cheap!

What you think Moses?  Is this an easy DIY?

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Sabueso...Well, you'll need to remove the differential cover and drain the fluid.  At that point you can tell what actually let go and why this issue has been plaguing your YJ Wrangler for a while.  If you have Trac-Lok, I'd be betting on a differential case that has separated, perhaps loose bolts that finally severed.  Otherwise, it could still be the differential or actual failure of the pinion shaft.  More likely the differential...

Post some photos (cell phone photos work) when you have the cover off and some sense for what broke.  It would be wise to raise the vehicle safely off the ground and place safety stands under the rear axle housing before removing the cover.  That way, you can easily rotate parts and do an inspection.

Rebuilding a rear axle does require care and following the guidelines for setting up the pinion depth, bearing preloads and the ring-and-pinion backlash.  You do need a professional level service manual for this work on your Dana 35 rear axle.  The manual will discuss tools needed and the procedure.  You can make an informed decision about whether you want to do the work yourself.  I am willing to provide tips and share safety concerns if you perform the work.

Glad you're okay and the vehicle did not lose control...Axles can be fixed.

Moses

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Thanks Moses.  Just for a heads up I will be posting pics soon.  I was able to open the cover.  One of the spider gears was completely in pieces and others were missing teeth.  I could also see the case with some damage and the ring is also missing a tooth or 2.

I'm busy this weekend but I can confidently do a complete tear down to share pics of how it blew up.  Once I get all the parts (new or used) it doesn't seem too difficult from what I've already read up on.  Except for the scientific tools and measurements.

Anyway, I will post soon and I will have questions about the install.  I think this will be a good post for others who experience loud clanking noises in their jeeps :D.

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Sabueso...I thought this would be a differential problem, and it is.  The broken spider gears likely ran through the ring-and-pinion.  This project is common and should be a big help to others...Looking forward to your photos.

You have an option now of changing the front and rear axle ring-and-pinion gear ratios, or you can just rebuild the Dana 35 rear axle with the same ratio as you have now.  You will need a new ring-and-pinion gear set and bolts, new differential parts, a bearing kit plus a new crush sleeve and seals.  (Time to replace the outer axle shaft seals, too.)  This is usually available as a "package" in the aftermarket.

You're right, this is a popular job!  The Dana 35 axle is light duty and found in the YJ/TJ Wrangler and XJ Cherokee.  Millions of these axles were built for Jeep vehicles.

Let's start a new topic with your next post.  A good working title would be "Rebuilding the Jeep YJ Wrangler Dana 35 Rear Axle"...

Moses

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Hi, I'm back with some pictures.  You can see the spider gears gone to pieces and in one photo you can see the case pretty chewed up.  Even the cross pin is bent (see pic).  Not even the ring was saved.  See if you can see the missing tooth.

There was a bolt/screw that releases the cross pin.  this one broke off as I removed it.  Per on-line forums and videos it could have been a major headache for some.  But luckily for me it must have been already broken so I was able to un-thread the remaining portion easily.  Just thought I'd mention that for others.  Before going at with bolt extractors or drills and such, try to see if you can turn the remaining piece slowly until its out.  Mine was there for 27.5 years.

Due to budget I've already purchased a complete used set that came from another Jeep with the same ratio.  My buddy Jeep guy also had spare differentials but his price was higher (good friend).  I'm waiting for it to arrive.

I read all over the internet how the Dana 35 can last and last or just blow up!  Being that mine lasted so long on low tires I'm thinking (and my wife is sure!) that the 33" x 12.50 tires was the cause.  They are so heavy for the 2.5.  Many others say the same.

 

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Well, Sabueso, that would cause a lot of banging!  You're very right about the gear ratios and tire sizing.  My son-in-law's 1987 Jeep YJ Wrangler had a 2.5L and 33" tires before I installed a 4.0L MPI inline six engine.  A previous owner had the good sense to install 4.88 gears; some do 4.56:1, the 4.88s place the least load on the powertrain.  

I installed an ARB Locker at each end of the YJ Wrangler, and we stayed with the Dana 35 axle and 33" tires.  Axle shafts were upgraded to Superior Axle shafts at the front and rear (30-spline upgrade).  The 4.0L engine and 33" tire diameter work better with 4.56 gears, which I installed with an AX15 transmission upgrade and an NP231 transfer case upgrade in place of the original NP207 that AMC/Jeep used behind the AX5 transmission.

The cross pin retainer bolt is a notorious trouble area.  Often, the bolt will break in service and send the hardened bolt head through the gears—which wind up looking like yours!  Subject to cross pin load and corrosive oil, these bolts are brittle and can be ultra tight coming out.  I use an air impact gun and prudence to remove these bolts and have better luck with carefully applied impact force than trying to twist the bolt out with a socket and ratchet.  Using air tool force, try to slightly tighten the bolt before backing it out...Use medium strength (blue) 242 thread locker on the new OE replacement bolt's threads for both anti-seize effect and to secure the bolt.  Torque the OE replacement bolt to specification, no more.

Note: There are specialty tools for removing a broken pin retainer bolt.  Here's one example for Ford and G.M. axles.  Dana repairs are likely addressed by some tool maker.  Left hand drill bits can often catch the bolt and screw it out.  We can discuss this further if anyone wants to open a topic on the subject.

Are you setting up the ring-and-pinion gears inside your original axle?  If so, please start a new topic thread on rebuilding the Dana 35 axle.  You'll need to set the pinion depth, the pinion bearing preload, carrier bearing preload and the ring-and-pinion backlash.  Always use a new pinion crush sleeve and do not crush the sleeve too far when setting the pinion bearing preload.  If you do go too far, do not loosen the pinion nut and leave a "loose" pinion crush sleeve in place.  Install another new crush sleeve!

Caution:  The pinion bearings require the correct preload with the crush sleeve pressing tightly behind the bearing.  Often, an installer will tighten the pinion nut too far and instead of starting the process over again with a new crush sleeve, they leave a loose sleeve in place.  The only right way to remedy this is with another new crush sleeve.  My son-in-law's 4.88 gears had a loose crush sleeve.  The previous owner or gear installer had backed the pinion nut off and thought that Loctite 242 would keep the nut in place.  This is a dangerous situation, since the pinion nut can back off under load, loosening the pinion shaft and wreaking havoc.  You can do this job with one new crush sleeve if you take care to bring the pinion bearing preload to specification very slowly, checking preload with each movement of the (new) pinion nut.  A quality bearing/rebuilding kit always includes a new crush sleeve, new pinion nut and new pinion seal.

Always use a factory equivalent workshop manual when setting up the ring-and-pinion gears.  Keep track of the shims and their locations.  The carrier bearing caps must go back in their original positions and face in the original direction.  These caps are match-machined to the axle housing's saddles.  Do not mix them or turn them around.  I always mark the caps with a pin punch dot(s) for both their location and the direction of fit.  If you tossed all of these parts into that pan without sorting them, try to recall their locations while your memory is still fresh.  

Before cleaning parts, you can usually match the bearing caps and their direction of fit to the axle saddles by following the oil/residue lines and markings.  Like a jigsaw puzzle.  If you're installing a used carrier and ring gear into your original axle housing, use your original bearing caps.

Moses

 

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After setting the pinion bearing preload, carrier bearing preload and the ring gear backlash, paint the ring and pinion teeth with axle testing paint.  A local motor supply may have this available, or you can use yellow titanium dioxide paint.  Since you're working with used parts, the goal is an exact tooth contact match with the worn-in teeth.

This is the final test with any ring-and-pinion gear setup.  A tooth contact pattern plus the correct bearing pre-load settings on the carrier bearings and the pinion bearings are your goals.  Do this to factory specifications...

Moses

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