| Independent Rear Suspension Technical Bulletin | |
| We have
recently been made aware of two aluminum rod-ends breaking (out of
roughly 350 IRS units) on the lower control arms of the Independent Rear
Suspension. We have sent the broken parts back to the manufacturer
to determine the cause and prevent any further failures. What we
have found is that it is possible for the rod-end to be positioned so
that it binds against the shims as it moves through the suspension
travel. This only happens if the jam nut has been tightened with
the rod end twisted from vertical at ride height and the larger shims
are in a certain position. If the shims are forced into place they
can also cause high loads on the shaft of the rod ends. In order
to ensure that this does not happen we are doing three things.
First is the larger shims must be replaced with smaller washer type
shims. The shims should be installed between the mount tabs to fit
snug, only using as many shims per side as fit without any force.
Replacement can be done after the car is aligned so as not to make that
process any more difficult. Second, the jam nuts must be tightened
for the final time before any driving is done and the rod ends must be
vertical when the car is at ride height (pictured below). Finally,
just to be certain that no damaged rod ends are out there, we are
replacing all of the aluminum parts with steel parts. We will be
sending out pieces to all customers in our database who own the IRS, if
you are not the original customer, and are not in our database, please
contact us. (508-291-3443)
Jim Shenck |
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INCORRECT Rod end mis-aligned |
CORRECT Rod end aligned |
| IRS Shim Replacement Procedure | |
| If you are careful and turn the new rod ends in the same number of turns as the old ones came out, your alignment will still be close. Even if you have the car re-aligned, this will make it much easier on the alignment shop. | |
| 1.
Place the rear of the car up on jack stands and remove the rear wheels.
2. It is easiest to do one side at a time. Count the number of shims on the front side of the front rod end on the lower arm. 3. Remove the bolt and shims that hold in the front lower mount and replace the rod end. 4. Replace the bolt using the same number of the washer style shims on the front as the old ones and as many shims toward the rear as fit without being forced. 5. Remove the bolt and shims from the rear mount and replace the rod end. 6. Replace the shims with the new ones. The number of shims will be determined by the position of the rod end and the shims should not be forced into position. The number of shims on either side of the rod end will change if your alignment changes. 7. Replace the upper rod ends re-using the old spacers. 8. Once the shims are in place, tighten all the mounting bolts and make sure that your rod ends are aligned vertically as in the picture and the jam nuts are tight. |
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