Trailing Arm shim part #

[Kevin M.]

I can't read the AIM, looks like 3846553-5-7-8.
Joe if you see this, any chance this is not discountinued and I can still get them at the GM parts counter?

Kevin

[Michael W.]

Re: Trailing Arm shim part #

Hollywood,

Even if you can get them at the GM counter, you probably don't want them because of corrosion issues. Just buy the stainless steel equivalents, I bet Joe Ray has them.

Mike

[Kevin M.]

Re: Trailing Arm shim part #

Yea looking locally today. I need to replace my rear strut rod bushings today, at the same time I wanted to get rid of the slotted shims in the trailing arm too. If I can get the guy to do just bushings I'll wait. Leaving for West Regional Wed and was hoping to button this up today or tomorrow. As far as rust goes I'm a west coast car, the rest of the shims on the car are factory and doing fine.

Kevin

[Kevin M.]

Re: Trailing Arm shim part #

Looking through my boxes of original parts I came across my original shims. Now if only the current specs match I'll reinstall.

Kevin

[Joe L.]

Re: Trailing Arm shim part #

Kevin------

The shim part numbers that you mentioned are the "2 hole shims". They're long-since GM-discontinued and replaced by the slotted shims. The "2 holers" are available in reproduction, though, for those folks so doggedly committed to originality that they forego "a major dose of functionality" for a very minor, virtually indiscernable "smidgeon of originality".

The GM slotted shims are as follows:

3983392----1/4" thick
3983393----1/8" thick
3983394----1/32" thick
3983395----1/64" thick

The above are, of course, mild steel type shims. Even though mine is a California car too, I prefer stainless, but the choice is yours on this one.

Beware of stainless shim kits, though; all are NOT created equal. Some of the kits omit the 1/4" thick shims and have you use more of the thinner ones, instead. I don't like that approach. The kits manufactured by Bairs have original thickness shims.

[Joe L.]

Addendum

By the way, a few other things that I failed to mention:

1) The GM shims are not cheap, at all. If you're buying a full car set you could be talking well over $100, even at discount GM prices. These shims are sold PER EACH, and NOT as a set from GM. Each one carries a list price of about 7 bucks.

2) The reason for my favoring the shim kits which include the 1/4" thick shims is not entirely one of originality, although most Corvettes came with at least one 1/4" thick shim on each side of each bushing. My reason is that the 1/4" thick shim is the most advantageous one to pound in after establishing the correct shim pack. A tight shim pack is very important and the last shim should be pounded in place. To do this, you remove the 1/4" thick shim, add the last thinner shim, then pound in the 1/4" thick shim. If you attempt to pound in the thinner shims, they'll usually bend; the 1/4" thick shim will not.

[Kevin M.]

Re: Addendum

Joe,

Very interesting, my cars current pack is made up of mostly very thin shims. I did find my original factory packs, Jerry B saved them for me. I have the 1/4" ones your talking about. I can't check them now but will in the future to see what I can use from original and what I would need to buy. I'm no expert but the pictures I posted elsewhere of my current pack received mixed reviews on whether or not holed shims verses slotted were safer and should I change. Could have been the shop too, not having proper thickness shims and making up with what they had.

Kevin

[Joe L.]

Re: Addendum

Kevin-----

If the following is done with the slotted shims:

1) Make sure that you have a tight shim pack by pounding in the last shim;

2) Tuck the shims down into the frame cavity;

3) Tighten the trailing arm forward bolt to specification and install the cotter pin (after the weight of the car is on the suspension and the suspension normalized);

You will have problem, at all, with the slotted shims "falling out". There is absolutely no need, whatsoever, to add the long cotter pins as used for 1970+ models.