68 trailing arm bolts.

[Terry F.]

Hi, I have been slowly restoring my 68 corvette for a number of years. I am having a problem with my trailing arm bolts that insert throught the frame. I kept track of the shims and put them back as they came out. But, when I inserted the bolt on one side and tightened down the castle nut, the nut went past the point at which the cotter pin should be inserted.

I have a total of 5/8 inch worth of shims on the left side and 3/4 inch worth of shims on the right. The shims look original, about a total of three on each side.

What do you suppose happened? Did one side get shorted shim stock at the factory and then get over tightened to take up the slack. Has anybody seen something like this before? I can make a tool I supose and pry the width back into that area and add another 1/8 shim in there. Or, I could just add another plate washer to the bolt to take up the slack in the bolt length. I hate doing things half ass. I would appreciate some comments on the issue. Best regards, Terry.

[Chuck S.]

Re: 68 trailing arm bolts.

Terry, you should have a total of 3/4" of shims on each side. My car had a total of six 1/8" shims for each control arm.

Here's a test that will probably verify if the shims are original: Prior to late 70, rear shims had full holes on each end, but later production and service shims are "slotted" on one end which allowed the shims to be changed without removing the control arm bolt.

If your shims have holes on both ends, they are probably the original shims. It is more likely that a shim was "lost" during an alignment, rather than being omitted by the factory. The best course is to install another shim. There should be a LARGE cotter pin that passes through the holes in the shims on both sides of the control arm.

[Terry F.]

Re: 68 trailing arm bolts.

Chuck, thank you for the responce. Looks like I will be taking that side apart. My shims have the large holes on each end. So, that sound good. I need to find me an 1/8 shim. I have looked for the little hole that the large cotter pin slides trough but have not been able to find it in the frame. My shims were all hanging down. Somebody was in there in the past.

I am worried about what it will take to spread the frame in that area. I can probably make a tool to force it apart. I wonder if there is a kind of small hydraulic jack I could stick in there and spead it 1/8 inch. It is only a tad loose now. I am sure it can be spread since it was squeezed by somebody tightening the bolt with out the shim. I could make a tool out of a long bolt and then heat the inside with a torch. I just need to probably make up 1/6 of an inch to get an 1/8 in shim in place. If this sounds crazy, let me know. Terry

[Terry M.]

Re: 68 trailing arm bolts.

I don't believe 1968s had a hole for a cotter pin, although I should know better than to post anything about 1968. That hole started during 1969 production, but the cotter pin wasn't installed in production until very late 1970.
Body shops have a small jack that will go in there to spread the frame - part of a Port-a-power tool. I suspect you could do the same thing with a threaded rod with nuts installed inside the frame pocket, especially if you could get some SAE, or fine, threaded rod.

[Harmon C.]

Re: 68 trailing arm bolts.

I haven't tried it but 1/2' threaded rod and some large and small flat washers shold make a spreader to push it out. Measure the complete package and make a tool to tell when you have went far enough. I would first try to put a wedge between two i/8 shims as I have many times drove the last shim in.You may find you have room to get the shim started and that is all it takes. Lyle

[Dave F.]

Re: 68 trailing arm bolts.

Terry,

There were no holes on my 68 for cotter pins. As for posts on 68's, I wish there were more. Tricky year at best, and I have found that there is no such thing as too much information available. In fact, I wish a collaborative existed for 68's only where all nuances could be organized and documented.

[Terry F.]

Re: 68 trailing arm bolts.

I feel better already. I will make a spreader with a bolt and attempt to move it without any heat. If I move it, which side should I put the extra shim into. I put the shims back the way I found them. I supose it's just a guess. The outboard side only has one shim, so I guess I will put it on that side. Any comments on this would be appreciated. Any body have an 1/8 inch shim laying around that they want to get rid of? Everybody, thanks for the suport. It has been helpful. If you only new how much this car has gone through. It has been an experience. Buba was everywhere. I go back to work for a couple days so it will be a while before I can attempt the job. Thanks, Terry

[Dave F.]

Re: 68 trailing arm bolts.

Terry,

I bought all new shims for mine, so I think I have the old ones still at the shop. I am traveling this week, and won't get back to my shop until Saturday. If you still have a need, email me and I'll get them to you.

Dave

[Chuck S.]

Re: 68 trailing arm bolts.

Terry, sorry for the misinformation on the cotter pin. Thanks to Terry McManmon for keeping things between the ditches.

You can try putting the shim on the side that moves the most when you spread the pocket (Sight across your thumbnail. ), but you will need to have an alignment done when you are finished.

You could check your Chevy dealer for the shim. Its highly likely they won't have them and can't order them either, but it's worth a try. Otherwise, you will have to shop the Corvette vendors, and will probably have to buy an entire shim kit. Shims from GM, or most vendors for that matter, will be the slotted style and not like your originals.

[Paul B.]

Re: 68 trailing arm bolts.

If you "make" a little all thread spreader bar, you'll have to use a size 7/16" OR if you want to go 1/2", you'll have pull the body off of the frame to drill the holes from 7/16" to 1/2".

[Joe L.]

Re: 68 trailing arm bolts.

Terry-----

1) You can very likely spread the frame pocket simply by driving in the last shim (a 1/4" thick one) with a hammer;

2) I DO NOT RECOMMEND the use of original style, "2 hole" shims. It makes the alignment shop's job much more tedious (and much more costly for you). You may even get an inferior alignment because the shop will be inclined to settle for "good enough". You can't get the "2 hole" shims from GM; they only have the "slotted" style which replaced the "2 hole" style for all applications:

3) The cotter pin was NEVER used for retention of shims in Corvettes (64-69) with "2 hole shims"; it was completely unneccessary for "2 hole" shims. You don't need to drill holes for and use the cotter pin for retention of the "slotted" shims if youy convert to them. Use a tight shim pack and tuck the shims down into the frame pocket like they're supposed to be (but, often were NOT from the factory);

4) I recommend ONLY the use of stainless steel shims; originality be damned in this case. I hate rust. If you use these, you can buy the whole kit from the various vendors. I like the kits that come with ALL of the original shim thicknesses. Not all of the kits do;

5) If you want to use stock GM shims (with slots on one end, of course, and of mild steel), you can still get them from GM under the following part numbers:

GM #3983392-----1/4"

GM #3983393------1/8"

GM #3983394------1/32"

GM #3983395------1/64"

The above-referenced shims GM list for $6 to $8 EACH, so you may be better off buying a whole kit from the reproduction sources.

[Harmon C.]

Re: 68 trailing arm bolts.

Good job on bolt size!! You could grind the threads down on the ends and sneak it in from inside. Lyle

[Terry F.]

Re: 68 trailing arm bolts.

Nice cars! I will play with it in a couple of days. I have 4 days coming off. I should get something worked out. I am slow and careful. My car is a dark blue/dark blue 68/390hp. I have been restoring it for too long. But it will be a nice car when done. I was starting to tighten things down when I ran into this problem. I will post a picture of my car when it is done. It has a long ways to go, but I might finish it this summer if my luck holds out. Terry

[Terry F.]

Re: 68 trailing arm bolts.

Thanks Joe, you always seem to have sound advice. Best regards to everyone. I will let you all know how it turns out. Terry

[Harmon C.]

Re: 68 trailing arm bolts.

Terry You said you need one 1/8" shim but you really need to buy a shim kit as the different sizes may be need by your alignment shop to do a correct job. In looking for a shop look for gray hair old equiptment and a person with old Corvette knowledge and get a per hour price as you want the job done right which can take extra time, not for $59.95 its out the door good enough. Lyle