Question 1968 rear control arm play
Thread Starter
Intermediate
Joined: Jun 2007
Posts: 33
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From: Iowa
Question 1968 rear control arm play
I have a 1968 Corvette convertible, 427. I have attached a couple of pictures of the rear control arm area. The driver's side seems very loose and too much play in the tire. If you jack the car up and grap the rear wheel at the top and bottom, it seems to have too much slop in it.
Any ideas on a fix, does this look OK?
Thanks
Any ideas on a fix, does this look OK?
Thanks
Team Owner
Joined: May 2001
Posts: 87,404
Likes: 1,595
From: Western NY
Your pictures are "zeroing in" on the front of the control arm, however you say that when you grab the tire you have play. Is this play at the pivot bolt at the nose of the trailing arm?
If so, in short, there shouldn't be any there. It probably means that when the car last had an alignment, the proper amount of shims weren't "packed" in between the arm and the tabs on the frame. The rear "toe in" is set by moving the shims between both sides of the bushing until the correct toe is achieved.
Maybe there was a shim missing, or one rusted out, but not replaced, creating the "slop"....
Most of the Corvette suppliers stock replacement shims in stainless steel.
If so, in short, there shouldn't be any there. It probably means that when the car last had an alignment, the proper amount of shims weren't "packed" in between the arm and the tabs on the frame. The rear "toe in" is set by moving the shims between both sides of the bushing until the correct toe is achieved.
Maybe there was a shim missing, or one rusted out, but not replaced, creating the "slop"....
Most of the Corvette suppliers stock replacement shims in stainless steel.
Race Director
Joined: Dec 1999
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From: Forked River NJ
Those shims are not in far enough. They should be inside the pocket, not sticking out like yours. This will not have any problem with the movement you are talking about but the shims could come out.
Team Owner
Joined: May 2001
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From: Western NY
Le Mans Master
Joined: Jan 2000
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From: New Hill NC
Look for wheel bearings or stub shaft clip missing.
Race Director
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Racer
Joined: Dec 2004
Posts: 410
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From: Wichita Kansas
Have someone move the wheel and watch the stub shaft where it goes into the differential. If you can see it move more than 1/8inch the snap ring clip has broken.
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Thread Starter
Intermediate
Joined: Jun 2007
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From: Iowa
Thanks for all the respones. Here is a little more info.
There is no play on the wheel bearing assemblys and all the movement is at the front arm bushing area. Yes these are the original style alignment shims and they are positioned correctly, the newer style ones are slotted.
There is no play on the wheel bearing assemblys and all the movement is at the front arm bushing area. Yes these are the original style alignment shims and they are positioned correctly, the newer style ones are slotted.
Race Director
Joined: May 2006
Posts: 16,528
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From: Dayton, Ohio
Thanks for all the respones. Here is a little more info.
There is no play on the wheel bearing assemblys and all the movement is at the front arm bushing area. Yes these are the original style alignment shims and they are positioned correctly, the newer style ones are slotted.
There is no play on the wheel bearing assemblys and all the movement is at the front arm bushing area. Yes these are the original style alignment shims and they are positioned correctly, the newer style ones are slotted.
Instructor
Joined: Nov 2002
Posts: 175
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From: GRIMSBY N.E.LINCS. U.K.
Looking closely and zooming in on your "DRIVERS SIDE" photo......
There seems to be about 1/2" to 3/4" gap between your thick inner shim and the outer facing side of your arm suggesting there are shims missing , allowing the arm to slide back and forward, you may have heard clunks from that when driving and rear shimmy on the rear wheels,this will not do the retaining c-clip on the end of the diff yokes one bit of good so check by leverage they or it are not sliding out more than 1/8" max, if they/it do the c-clip is bust or yoke ends have worn down against diff pivot shaft and c-clip has fallen off.(search the forum for more info.)
Strange they could be missing that thickness dont think rust! as these shims are retained on the arm pivot bolt shaft by a hole and not a slot there should be traces of bust shims still aroud shaft within the pocket,more likely some wrong style slotted shims may have got in there and just shimmy'd there way out.Also looks like the cotter pin is missing too sugesting nut may have backed off a little and slotted shims would have slid out especially if they were left overs from another vehicle not especially a vette.
There seems to be about 1/2" to 3/4" gap between your thick inner shim and the outer facing side of your arm suggesting there are shims missing , allowing the arm to slide back and forward, you may have heard clunks from that when driving and rear shimmy on the rear wheels,this will not do the retaining c-clip on the end of the diff yokes one bit of good so check by leverage they or it are not sliding out more than 1/8" max, if they/it do the c-clip is bust or yoke ends have worn down against diff pivot shaft and c-clip has fallen off.(search the forum for more info.)
Strange they could be missing that thickness dont think rust! as these shims are retained on the arm pivot bolt shaft by a hole and not a slot there should be traces of bust shims still aroud shaft within the pocket,more likely some wrong style slotted shims may have got in there and just shimmy'd there way out.Also looks like the cotter pin is missing too sugesting nut may have backed off a little and slotted shims would have slid out especially if they were left overs from another vehicle not especially a vette.
Last edited by SARASOTA SAM; Sep 29, 2009 at 10:17 AM.
Thread Starter
Intermediate
Joined: Jun 2007
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From: Iowa
Thanks for all the respones. I want to clarify that the movement seems to be in the control arm itself where it is bolted to the frame by the shims. Both sides move a little bit, but the driver's side is really bad. The control arm itself is what moves, it actually twists. Is it possible there may be an issue with the bushing? Most of the parts look new though.
Thanks
Thanks
Tech Contributor
Joined: Aug 1999
Posts: 15,187
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From: Connecticut, USA
Could very well be the bushing. I've found some new bushings are poor quality, other times I've had arms in to rebuild and found new bushings that were not correctly compressed and flared.
The also could be a rip in the arm but that is not too common, and usually shows up in the rear section where water rots them out.
The only way to know for sure is to remove the arm for a closer look. If you look up my thread on T/A's it shows a correctly installed bushing.
The also could be a rip in the arm but that is not too common, and usually shows up in the rear section where water rots them out.
The only way to know for sure is to remove the arm for a closer look. If you look up my thread on T/A's it shows a correctly installed bushing.
Instructor
Joined: Nov 2002
Posts: 175
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From: GRIMSBY N.E.LINCS. U.K.
The only way i can see it twists is that shims are missing, it should be packed tight without forcing on both sides with shims.
If shims are missing you can get a twist on the bushings especially if they are bad or lose. Missing shims will destroy the bushings quickly make the back end unstable destroy tyres and bearings etc and make car dangerous.
If shims are missing you can get a twist on the bushings especially if they are bad or lose. Missing shims will destroy the bushings quickly make the back end unstable destroy tyres and bearings etc and make car dangerous.
Race Director
Joined: Jul 2001
Posts: 15,892
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Thanks for all the respones. I want to clarify that the movement seems to be in the control arm itself where it is bolted to the frame by the shims. Both sides move a little bit, but the driver's side is really bad. The control arm itself is what moves, it actually twists. Is it possible there may be an issue with the bushing? Most of the parts look new though.
Thanks
Thanks
Can you move the trailing arm side to side?. Y/N
If yes, you have shims missing or similar issues with the way the shim pack has been assembled. If no, and the only motion you can induce is torsional motion (twisting) then you need to determine what is ALLOWING the trailing arm to twist. Investigate the differential yokes or strut rod bushhings.
The front bushing does not control or prevent the trailing arm from twisting. Rubber was used to permit a limited amount of twisting as the suspension goes through it's normal range of travel. IE- you're presently looking at the wrong area for the wrong reason.
Team Owner
Joined: Mar 2002
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It is rather telling that he's able to rock the wheel by hand at 12 & 6 enough to see motion at the t-arm nose. That would seem to indicate that the strut rod bushings and stub axles are worn out as well.
Thread Starter
Intermediate
Joined: Jun 2007
Posts: 33
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From: Iowa
Looks like we may have found the problem. Whoever installed the bushings originally, did not do them correctly. They are suppose to mushroom out around the bushing when pressing them in to the control arm, and they are not.
Thanks for the help!
Thanks for the help!
Tech Contributor
Joined: Aug 1999
Posts: 15,187
Likes: 4,008
From: Connecticut, USA
Glad you found it, as mentioned I've found that as well. Be sure the bushing is good or just replace it, compress,flare and check the hole ID. Some bushings on the market are pretty cheap, with problems with the sleeve ID, flare,and fit - be sure you use good parts.
