66 Rear alignment shims

[Ed K.]

Help!!! I'm rebuilding the entire rear of my 66. I cannot get the old shim thickness to fit. I believe that the new rubber bushings are not compressed enough, but not sure if that's the problem. I have some slotted shims and tried installing a thin one between the bushing and chassis. Then I expected to hammer a thick one between the thin shim and chassis, thereby crushing the new bushing. But not having any luck. I realize 66 shims do not have slots - just using those now until I get the car together and take it for an alignment.

I've never used this discussion board before. Hopefully I've done it correctly. Thanks, in advance

[Wayne W.]

Re: 66 Rear alignment shims

You should not have to do any hammering. If you fill the opening, when you tighten the bolt it will collapse the sides of the frame enough to capture the shims.

[Michael H.]

Re: 66 Rear alignment shims

I believe that the new rubber bushings are not compressed enough, but not sure if that's the problem.

If you think there may be an issue with the installation of the bushings in the control arms, NOW is the time to correct this.
It's very important that the bushings be installed and compressed correctly before the center tube is flaired. If not, you will have shims falling out randomly until you completely disassemble the rear suspension again and properly install the bushings.
Some special tools are required to properly install the bushings.

If you find that the original shim stack no longer fits after your new bushings are installed, that would be a good indication that the new bushings are NOT installed correctly.

There's a lot of good information in the archives on this subject.

[Ed K.]

Re: 66 Rear alignment shims

You're absolutely correct in suggesting I check the bushings now before completing the assembly. The bushings are the only thing that changed - chassis rails arms, shims could not change. The arms were rebuilt by a local Corvette resto shop that I believe knows what they're doing. However, #$%^ happens.
Would you know how to confirm the bushings are corrctly installed? The shop manuals for 1966 and 1964 both just simply state "Continue threading J-8111-23 until retainer is flared.
Also, previous owner told me one side was re-shimmed in 1983 by a reputable shop. Those shims are in "new" condition. The other side may be original - badly rusted. Not sure how to interpret this.
Ed

[Michael H.]

Re: 66 Rear alignment shims

You're absolutely correct in suggesting I check the bushings now before completing the assembly. The bushings are the only thing that changed - chassis rails arms, shims could not change. The arms were rebuilt by a local Corvette resto shop that I believe knows what they're doing. However, #$%^ happens.
Would you know how to confirm the bushings are corrctly installed? The shop manuals for 1966 and 1964 both just simply state "Continue threading J-8111-23 until retainer is flared.
Also, previous owner told me one side was re-shimmed in 1983 by a reputable shop. Those shims are in "new" condition. The other side may be original - badly rusted. Not sure how to interpret this.
Ed

Ed..

If you have the 66 service manual, page 4-20 describes the operation. (pic's on page 4-22)
Before the center tube is flaired, the inner steel portion/tubes of the bushings MUST be pressed together so they make contact with each other.
If the inner sections are not in contact when the center tube is set/flaired, it's not possible to secure the assembly using the control arm pivot bolt. The bushings will rotate and the shims will fall out. Guaranteed.

We've seen this issue many times over the years. Many folks don't understand how this system works and feel that if the bushing is compressed "a little bit", it's good enough. Unfortunately, it's not.

You may be able to fabricate a tool to compress the bushings completely while flairing the tube.

If someone happens to have a new bushing, maybe we can get a few pic's and show that the inner sleeve is not at the same level as the outer sleeve before being pressed together. There's probably a 1/16" difference in this dimension. When the assy is pressed together properly, the inner and outer sleeve will be at the same dimension and the inners will make contact with each other.

Sorry, this is really difficult to describe. Look at the pic's in the manual.

[Joe L.]

Re: 66 Rear alignment shims

You're absolutely correct in suggesting I check the bushings now before completing the assembly. The bushings are the only thing that changed - chassis rails arms, shims could not change. The arms were rebuilt by a local Corvette resto shop that I believe knows what they're doing. However, #$%^ happens.
Would you know how to confirm the bushings are corrctly installed? The shop manuals for 1966 and 1964 both just simply state "Continue threading J-8111-23 until retainer is flared.
Also, previous owner told me one side was re-shimmed in 1983 by a reputable shop. Those shims are in "new" condition. The other side may be original - badly rusted. Not sure how to interpret this.
Ed

Ed-----

It's easy to discern if the bushings were compressed enough. Just look at the trailing arm from the forward end. Check for this:

1) The flange of the bushings are fully seated against the outer and inner surfaces of the trailing arm, and:

2) The inner end of the bushing steel shells are contacting one another (or VERY close to contacting one another, maybe 1/32" or less from contact).

If the above conditions exist, bushing compression is not a problem.

[Michael H.]

Re: 66 Rear alignment shims

The bushings are the only thing that changed - chassis rails arms, shims could not change. Ed

Here's a drawing that shows how the inner sleeves of the bushings are in contact with each other. If the bushings are not pressed together, and the sleeves do not actually make contact, the sleeve will rotate with the control arm as it moves/rotates up/down through normal suspension travel range.

You may be able to use two steering wheel pullers to compress the bushings, one on each side. You will know when the inner sleeves make contact with each other as you tighten the bolts on the pullers. the bushing will suddenly stop compressing. Then insert and flair the center tube.

[Gary R.]

Re: 66 Rear alignment shims

I do custom t/a work and can tell you not all the bushings are the same. The quality varys from to good to bad. Measure the thickness of yours to see where they are. Chances are slim you're going to get the new bushings to be exactly where the originals were,that does not mean the installer did anything wrong. Here is a set I installed and use as a reference. Also check the bolt in them now,many of the cheap ones have smaller ID or crimped ID's so the bolts won't fit. You don't want to play games trying to fit a bolt when you have the arm in your hands later.

[Joe L.]

Re: 66 Rear alignment shims

I do custom t/a work and can tell you not all the bushings are the same. The quality varys from to good to bad. Measure the thickness of yours to see where they are. Chances are slim you're going to get the new bushings to be exactly where the originals were,that does not mean the installer did anything wrong. Here is a set I installed and use as a reference. Also check the bolt in them now,many of the cheap ones have smaller ID or crimped ID's so the bolts won't fit. You don't want to play games trying to fit a bolt when you have the arm in your hands later.

Gery-----


I agree completely. In fact, your second photos illustrates exactly what I was referring to in a previous post. The bushings may not come to be exactly touching (actually, they usually are touching but not necessarily at the area in their circumference that can be seen from the forward opening in the trailing arm).

I believe this is caused by "irregularities" in the bushing shells and/or very slight in-service distortion of the trailing arms. These bushings are definitely not what could be described as a "precision" piece.

[Michael H.]

Re: 66 Rear alignment shims

Gery-----


I agree completely. In fact, your second photos illustrates exactly what I was referring to in a previous post. The bushings may not come to be exactly touching (actually, they usually are touching but not necessarily at the area in their circumference that can be seen from the forward opening in the trailing arm).

I believe this is caused by "irregularities" in the bushing shells and/or very slight in-service distortion of the trailing arms. These bushings are definitely not what could be described as a "precision" piece.

The sleeves that must come in contact with each other when properly loaded are the inner sleeves. The gap in the outer sleeves, visible in the pic's above, does change from one setup to the next, depending on the dimension (thickness) of the control arm.

If the inner sleeves are not butted together when installed, the assembly will not be stacked and the pivot bolt in the control arm will not secure the arm properly.

[Ed K.]

Re: 66 Rear alignment shims

Gentlemen: Thank you all for your input. Family obligations prevented my attending to this earlier today. I'm on my way to the garage now to remove an arm from the chassis. I have to be careful and find a way to support the weight of the arm while I juggle it around. Due to an artificial heart valve, I should not atempt to hold anthing heavy for too long a period. My son helped me install it but he's not available now.

[Ed K.]

Re: 66 Rear alignment shims

Heart valve challenged leads to new use for wheel shims..and milk crate..paint stirrer, but supports the arm assembly without strain for me. Please see attached photos. I think all looks OK except for rust that's beginning to form. Have to sand it out. But, now what?

[Wayne W.]

Re: 66 Rear alignment shims

Nothing wrong with that one. Just stack it full of shims and have it aligned.

[Michael H.]

Re: 66 Rear alignment shims

Heart valve challenged leads to new use for wheel shims..and milk crate..paint stirrer, but supports the arm assembly without strain for me. Please see attached photos. I think all looks OK except for rust that's beginning to form. Have to sand it out. But, now what?

The bushings do look somewhat compressed. Impossible to tell if the inner sleeves are in contact though.

[Ed K.]

Re: 66 Rear alignment shims

Thanks, but previously after I put shims in there seems to be a considerable amount of play. About 1/2" in/out at the axle center. I was able to begin hammering an 1/8" shim in but could not get the last inch in. I guess I just fill it with several thin ones? Should I be hammering? It's impossible to hammer the thin shims without bending them. AND most importantly... I greatly appreciate all the help.