Differential Cross Member Cushion Modification


​​To stabilize the rear end the way I wanted to, I needed to modify the cross member cushions.  The idea was to put a spacer between the cushion mount on the frame and the cushion to minimize cross member rotational movement front to back.  At the same time, I would cut off the lower portion of the cushion so the stabilizer disk pressed against the cross member, and not the cushion tabs and sleeve.  This would draw the cross member tightly against the cushion, and the cushion tightly against the spacer.  I'm not sure how good an idea this is, as I've not been able to find anyone else that has done this.


Here is the modified cushion.  I measured the depth of the sockets in the cross member and cut these 1/8" shorter.  That turned out to be right about where the tabs met the sleeve.  So I used a dremel with a cutting wheel to remove the tabs.  Then I used a handsaw to cut the rubber away and a flat rasp to level it out.  Finally, I used the dremel to cut the inner sleve back flush with the rubber.









I measured the inner and outer diameter of the cushion top. When taking that measurement, I used the outer diameter of the center rubber ring as the inner diameter for the donut spacer.  This ensured the ring would pass up through the spacer and allow the cushion to seat against the mount.  I gave those measurements to a welding shop and asked them to cut these out of some 1/2" scrap plate steel.  In the picture at right, I show these after I did some additional work and powder coated them to protect against rust.  The left spacer shows the side that goes against the cushion.  On the right, you can see where I had to make a bevel.  This was necessary due to the slight curve of the frame extension the cushion mount is welded to.  As you can see, they aren't pretty but they fit.


Finally, here is the stack assembled.  I used 7/16" 14 threaded rod to cinch the cushion to the frame mount.  This drew it up against the cushion before seating it on the mount.  I used blue thread locker to make sure it stayed in place.  Next I used a jack to put the cross member in place over the cushion and the stabilizer disks to draw the cross member tight against the cushion, and compress the whole stack.  I used blue thread locker here too. 






SUMMARY:  I would give this a 7 out of 10.  No one step was particularly difficult, but putting it all together between the spacer, the cushion mod, and the stabilization disks took a little figuring out.  I'm still not sure how well this will work, and intend keeping an eye on it for some time.  I believe these are fairly stable in the sense that they provide the counter force to the leaf spring so I'm not too worried about the cushion or cross member coming unseated if the threaded rod were to break.  I am concerned that the rubber may split, deform, and disintegrate over time.



Trailing Arms


After installing the differential cross member, I installed the trailing arms.  I didn't include any picture of this because it's very straight forward and not too exciting.  I used a stainless steel trailing arm bolt kit (bolt with castle nut, washer, and cotter pin) and stainless steel alignment shims.  I divided the shims nearly evenly, but made sure there was a little toe-in once everything was assembled.


Summary:  I would give these a solid 2 out of 10.  The trailing arm is cumbersome to work with and this job is definitely easier with help from a buddy.  The alignment shims can be difficult to install as well.  I did not torque these down because I will align the trailing arms later.



Strut Rod Bracket


After installing the trailing arms, I installed the strut rod bracket with the heim joint ends.  I've included the picture at right to illustrate how it looks with the aluminum spacer.  I purchased some grade eight bolts that were 1/2" longer than the stock bolts to compensate for the added thickness.  This bracket was torqued to specification and held in place with blue loc-tite.


SUMMARY:  This is also a 1 out of 10.  Four bolts properly torqued and you're done.




Half-shaft and Safety Hoop Installation


The half-shafts and safety hoops have to be installed together.  I installed the half-shaft at the differential end first.  I incorporated the improved u-joint end caps shown to the right.


Next I put the half-shaft through the safety hoop and attached it to the trailing arm flange.  I used stainless steel french locks.  








Before bolting on the safety hoop, I had to install the strut rods because the safety hoop attaches at the back side of the shock mount.


With the strut rod in place, the safety hoop attaches to the top of the trailing arm at the frame bumper contact pad and the bottom at the shock mount.  The completed assembly is shown at right.


SUMMARY:​  This is a 2 out of 10.  You have to do things in the right order.  Otherwise it's very straight forward.







​Next was the composite leaf spring.  I purchased the spring from VanSteel.  After speaking with their very helpful technical folks, they convinced me to purchase a slightly stiffer spring than I had planned based on the target torque of my engine build.  This spring rating is the same as the Gymkhana option.


Installation was a little tricky, but not too tough.  I attached the center plate and spacer first.  Do not torque the bolts until the spring is loaded with the car's weight.  I had pre-installed the out spring bolts on the trailing arms prior to mounting the sway bar bracket.  The cushions are location dependent and the directions not too clear on which go where.  The flat cushion goes in the trailing arm.


With the spring secured in the center, I was able to use a floor jack to lift the spring enough to get the bolt through.  I was concerned that the frame and suspension would not weigh enough, but it did.  The bolt can be difficult to get lined up with the hole, and it has a tendency to want to scrape along the spring.  If you are patient and move the bolt, raise the jack, move the bolt, raise the jack, etc., you'll get it.  Once the bolt is through enough to place the cushion, washer, and bolt on, you're on your way.  I will have to wait until the car is together before making ride height adjustments.


SUMMARY:  This is a 3 out of 10.  Any time a large spring is being compressed it's a little nerve wracking.  The main thing is to get the cushions correct and manipulate the bolt through the hole so the threads don't scrape along the edge.

Back to Rear Suspension                                    Progress so Far

Back to Rear Suspension                                    Progress so Far

Rear Suspension

​(Cont.)