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Member Spdljohn began a brake and chassis frame-off restoration topic that has now expanded into discussion of the use of a shackle reversal kit on a 1976-86 Jeep CJ-5, CJ-7 or Scrambler/CJ-8.  Below is the topic thread that member Spdljohn began...Join us and share your experience with the shackle reversal kit!

 

Moses

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I am going with an old man emu 3-3.5 inch suspension.  Looks like with that kit the front shackle support has to be moved forward about an inch.  Otherwise looks like that kit is plug and play.

 

I've heard conflicting reviews of the shackle reversal kit.  I bought the old man emu suspension from rocky road suspension (rocky-road.com).  They advised against shackle reversal with the idea being that jeep designed it the way they did for a reason.  They claim that under hard braking conditions with the shackle reversal there was instability that could lead to loss of control.

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As for the front shackle supports, since you have to move the brackets forward, this would be a good time to consider a front shackle reversal kit that puts the spring anchors at the front ends of the front springs.  The front axle then "trails" behind the anchors. 

 

The vehicle tracks better with the front axle trailing from the forward-mounted anchors—instead of the front axle being pushed down the road by OE rear anchors and the leaf springs.  When you encounter an obstacle off-road with the shackle reversal, the front axle will lift up readily instead of driving all the thrust into the frame at the OEM rear anchor positions before compressing (lengthwise) the springs and ultimately "popping" the front axle upward.  Since you're configuring the shackle position anyway, it is also practical to install reverse shackle brackets at this time and re-hang the shackles at the rear of the front springs. 

 

If you look at your OEM frame shackle brackets, they are a poor design.  AMC/Jeep punched a relief hole for clearing a frame rivet.  This relief hole also creates a weak area in the shackle bracket, and these factory bolt-on brackets are notorious for breaking or bending under load or during spring and axle articulation...another good reason for installing an aftermarket shackle reversal kit.  If you install a shackle reversal kit at the front end, take careful measurements to avoid altering the front axle location, wheelbase length or creating a front driveline length issue.  The front driveshaft must be able to extend and compress properly under full spring travel and articulation, without compromising the spline coupler engagement or bottoming the coupler under driveline compression.

 

As for loss of control under hard braking with a shackle reversal kit installed, I can't imagine how that would happen.  With a shackle reversal kit installed, braking would pull the frame to a stop as the front axle and brakes apply.  Force would be pulling at the front mounted frame anchors in the same way the rear braking currently works. 

 

With the OEM anchors at the rear end of the front springs, the front axle and brakes slow the vehicle by applying force rearward through the leaf springs to the anchors mounted to the frame at the rear end of the front springs.  In these two scenarios, I'd take my chances on brakes that slow the frame in a pulling fashion, rather than brakes that slow the vehicle by applying force through the aft ends of the front leaf springs. Shock absorber design and choices play a role here, too.

 

There is also the question of a stabilizer bar.  On your CJ, the stabilizer bar helps keep the frame/body as level as possible on cornering.  During braking, the axle stays in lateral alignment due to the inherent design of leaf springs and their bushings—if the bushings are in good condition and of the right durometer or hardness. 

 

Many remove the stabilizer bar to avoid installing the necessary longer links required with a lift kit—or to increase the range of axle articulation, which can be facilitated by using quick disconnect stabilizer links when off-roading.  Quality lift kits include stabilizer bar quick disconnect links of the right length to compensate for the lift.  Without a stabilizer bar, the vehicle acts like a vintage Jeep 4x4 on the highway: Cornering stability relies strictly on the leaf spring resistance and the condition of the spring bushings, shackles and anchors.

 

As a point of interest, the 1987-95 YJ Wrangler uses a similar chassis layout to the CJ-7 yet adds a track bar along with the use of a stabilizer bar and links.  The track bar holds the front (or rear) solid/beam axle in a more precise lateral alignment as the axle rises and sets.  This contributes to better handling on-highway. 

 

Semi-elliptic leaf springs, by design, provide a higher degree of lateral stability.  Link-and-coil suspension (or single radius arm suspension like a Ford F150 4x4) requires a track bar to keep the front or rear axle from floating uncontrollably sideways or laterally. 

 

Moses

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Actually, Jeep did design the military M38A1 (prototype for the CJ-5) with front spring anchors at the front ends of the front springs.  The earliest CJ-5 was built on this frame.  My 1955 CJ-5 featured in the Jeep CJ Rebuilder's Manual: 1946-71 has this frame as stock equipment.  The U.S. military M38A1 or "MD" and its military export equivalent stayed in steady production from 1951 (began replacing the MC or M38 flatfender that year) until 1968, some units may have been built as late as 1971.

 

You're right about the rear shackle bracket being riveted to the frame.  The front shackle brackets bolt into place with the nuts in the frame being the notorious type that partner with "self-cutting thread" bolts.  This same approach was used by AMC on the skid plate frame nuts that often spin loose during bolt removal and require tack welding a new (i.e., real and graded) nut into the frame.  These bolt-threaded frame nuts were apparently a production time saver for pneumatic assembly line wrenches.  They required very hard (i.e., less ductile and more prone to snapping) self-tapping bolts and compliant frame nuts.

 

Note: Use care removing these shackle bracket and skid plate bolts, they often seize and snap during removal.  I soak frame nut threads with penetrant and use an air impact wrench/gun cautiously.  In my experience, hand wrench removal is more likely to twist the heads off these bolts.  Impact force can work to advantage if used properly.

 

For those who want to keep the stock shackle orientation, there are ways to upgrade the bolt-on front shackle brackets.  Years ago, as featured in my Jeep Owner's Bible, friend Kirk Rogers and I produced the Westfir Engineering front shackle bracket replacements that worked with the stock spring anchor positions.  These sturdy, extended brackets picked up the additional support of forward bumper bolt holes and provided added support forward of the bushing eyes.  This eliminated the OE "hanging out" eye end and overcame the stock bracket's glaring punch hole weakness at the frame rivet.  This bolt-on bracket provided additional support and worked well, substantially improving the front shackle mounting method.  We passed the sturdy design to Full-Traction Suspension, not sure whether they still offer this solution or preserved our original design.

 

Here are some currently available shackle reversal kits to review before making your decision:

 

1) http://www.4wheelpar...HEu0aApZk8P8HAQ

 

2) http://www.4wd.com/J...f8bwaAk4_8P8HAQ

 

3) http://www.4wheelpar...OrdsaAvUI8P8HAQ

 

These are examples, you'll get the idea.  Some incorporate a frame structural cross brace, which is not a bad idea with an LS V-8 installation.  In any case, there's an obvious market and reason for these kits.  Be aware that this is chassis work that requires several considerations:

 

1) The axle must be located in its original position.  I take measurements in "diamond" from front axle to rear axle and follow stock wheelbase measurements.  The precise wheelbase (wheel vertical centerline-to-centerline) for your 1981 Jeep CJ-7 is 93.4 inches.

 

2) Front driveline must not compress too far on upswing of the axle, as the arc is now from the front end of the springs, which takes the axle rearward as the springs flatten under compression.  Obviously, the splines in the front driveline spline coupler must be within normal range of travel within the coupler.

 

3) A quality kit should consider front axle caster adjustment.  Steering caster is critical, and final caster angle should be at least 4-degrees positive, some use up to 6-degrees for tighter "motor grader" turning and assured steering return to center.  Caster angle can be accomplished with proper spring arch and perch locations.  If  necessary, steel (not aluminum) wheel alignment wedges can be placed between the axle spring perches and the springs to rotate the axle housing for precise caster setting.  

 

4) These kits do require drilling and welding.  The welding should be done to professional grade, as this is a safety modification.  If the instructions are complete, the measurements for placement of the brackets and sleeves will be included.  You might seek out these instructions before committing to a shackle reversal kit.  If measurements are accurate, you still have the Old Man Emu lift spring concern about the 1/2-inch adjustment.  Take this into consideration before permanently positioning the brackets or rear frame sleeves. 

 

Note:  Some shackle reversal kits have a built-in lift like 1.5".  This would require a rear spring consideration, possibly installation of longer, heavy-duty rear shackles, followed by adjusting the rear axle pinion angle (steel wedges if necessary).  Be aware that any CJ lift in the 4"-plus range will require driveline length modifications.

 

5) Since the shackle reversal does require frame changes, make sure the approach is what you want.  "Restoring" to stock would be a fabrication chore later.

 

I have done the shackle reversal on both Jeep and Land Cruiser FJ40 chassis with great success.  In the case of an unquestionably short wheelbase (90") for towing FJ40, I did a reversal kit prior to pulling a 21' travel trailer.  With a load distribution hitch and anti-sway brake, this setup worked well in Mojave Desert crosswinds and on curvy roads.  The biggest gain is not pushing the front axle forward from OE rear spring anchors at the frame.  In my experience, the trailing front axle makes for more precise steering and reduced risk of wander.

 

Caution: I do not endorse or recommend pulling hefty or lengthy trailers with short wheelbase vehicles!  The Toyota FJ40 Land Cruiser was very short for this kind of trailering; however, it had a comparatively wider track width, more like a full-size pickup truck.  I chose the tow equipment carefully, and this '80s OFF-ROAD Magazine project had a lift kit, stiff springs, a Saginaw power steering conversion with one-piece draglink and a one-piece tie-rod, 10" wide (with negative offset) wheels and 33x12.5x15 tires to counter the lift kit's raised center-of-gravity.

 

When loss of control under braking is alluded, I often find that the steering linkage alignment is off.  Upon hard braking, there is bump steer or in this case veering caused by a radically sloping tie-rod or draglink that steers the vehicle (typically to the right in left-hand drive 4x4s with a beam axle) sharply and abruptly.  Steering linkage alignment over the range of axle travel is critical for preventing bump steer, regardless of the leaf spring anchor location.

 

If you install any one of these kits or another, please let us know whether the design and instructions clarify the mounting locations for the brackets.  Is the kit easy to set up and install?  The Old Man Emu springs must be longer than stock CJ if the front shackles require relocation.  Let us know how you resolve this with a shackle reversal if you do install a kit. 

 

Your photos are great.  Thanks!

 

Moses

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So I decided to go with a shackle reversal system from MORE.  Kit #7686-2 (fits the YJ springs).  This is not the bolt on application.  The bolt on application adds another 1.5 inches of lift.  The OME YJ lift already supplies 2.5-3 inches of lift and that is plenty for me.  The kit Im getting requires a hole be drilled through the frame and a spacer welded into place.  Ill let you know how it goes.  Should be getting the frame back from the sandblaster/welder late this week or next.

 

David

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