63 Rear Suspension Moves On Deceleration

[Daniel K.]

On deceleration, the rear end of the car seems to move to the right. I've looked at the half shafts and they seem to be fine, at least nothing there seems to be lose. Drive shaft also seems to be fine...nothing lose. I do hear a clunk when I let off the gas which seems to be concurrent with swaying motion of the car. Could it be the 3rd member? Thanks for your help.
Dan K.

[Jimmy B.]

Re: 63 Rear Suspension Moves On Deceleration

Daniel,

1st thing I'd check is that rear snubber bushing but I am sure others will chime in.

Good luck.

Jim

[Joe L.]

Re: 63 Rear Suspension Moves On Deceleration

On deceleration, the rear end of the car seems to move to the right. I've looked at the half shafts and they seem to be fine, at least nothing there seems to be lose. Drive shaft also seems to be fine...nothing lose. I do hear a clunk when I let off the gas which seems to be concurrent with swaying motion of the car. Could it be the 3rd member? Thanks for your help.
Dan K.

Dan-----


Besides the snubber bushings that Jim mentioned, I'd look at the following:

1) make sure the rear toe shim packs are TIGHT with all shims "present-and-accounted-for";

2) check the rear sway bar bushings for deterioration;

3) check ALL suspension fasteners for tightness.

[Bob B.]

Re: 63 Rear Suspension Moves On Deceleration

Dan, I agree with Jim on checking the snubber bushing. I had this problem on my 63 that I bought new in 62 and took it back to the dealer service department many times for a fix. (they never fixed, couldn't find problem) The bushing has tabs that are bend over onto the cross member to hold it in. When these tabs unbend (from power shifts and old age,yours) it allows the bushing to pull part way out of the member, then when you let off the gas it snaps back in place, that's the clunk. Mine was a early build #618 and the bushings had only two ests of tabs 180 degrees apart that didn't hold for long.(POWER SHIFTS) The car (that I still have) is a FI, metellic brake,no radio convert. Bob

[Wayne M.]

Re: 63 Rear Suspension Moves On Deceleration

....The bushing has tabs that are bend over onto the cross member to hold it in. When these tabs unbend (from power shifts and old age,yours) it allows the bushing to pull part way out of the member, then when you let off the gas it snaps back in place, that's the clunk. Mine was a early build #618 and the bushings had only two ests of tabs 180 degrees apart that didn't hold for long.

Dan -- In addition to Bob's experience, even if the tabs did not unbend, the factory spec on the 2 bolts that hold this differential X-member to the frame were WAY under torqued from the factory (25 ft.lbs versus 55 ft.lbs revision in 1965-up) so the bolts may be loose/fallen out.

[Steven B.]

Re: 63 Rear Suspension Moves On Deceleration

Dan, I agree with Jim on checking the snubber bushing. I had this problem on my 63 that I bought new in 62 and took it back to the dealer service department many times for a fix. (they never fixed, couldn't find problem) The bushing has tabs that are bend over onto the cross member to hold it in. When these tabs unbend (from power shifts and old age,yours) it allows the bushing to pull part way out of the member, then when you let off the gas it snaps back in place, that's the clunk. Mine was a early build #618 and the bushings had only two ests of tabs 180 degrees apart that didn't hold for long.(POWER SHIFTS) The car (that I still have) is a FI, metellic brake,no radio convert. Bob

Bob, sounds like a very special Corvette! Can you please post pictures?

Thanks!

Steve

[Alan D.]

Re: 63 Rear Suspension Moves On Deceleration

If you have not found the source yet check the front Mounting Bracket bolts. The 63/64 brackets typically had ware on the front two bolts which caused GM to make changes to a better bracket. Needed to replace mine back in the late 60's with one which had a built up shoulder for the two front bolts. know a lot of friends who also had early problems with these before the new part became available.

[Joe L.]

Re: 63 Rear Suspension Moves On Deceleration

If you have not found the source yet check the front Mounting Bracket bolts. The 63/64 brackets typically had ware on the front two bolts which caused GM to make changes to a better bracket. Needed to replace mine back in the late 60's with one which had a built up shoulder for the two front bolts. know a lot of friends who also had early problems with these before the new part became available.

Alan-----


Yes, the holes can become elongated in the 63-64 front differential carrier mounting bracket. If they become elongated, this can be a source of the "clunking" problem. The only way to repair this is to weld the holes up and re-drill or weld on reinforcing plates or washers as was done for later model years.

[Joel T.]

Re: 63 Rear Suspension Moves On Deceleration

Dan, I agree with Jim on checking the snubber bushing. I had this problem on my 63 that I bought new in 62 and took it back to the dealer service department many times for a fix. (they never fixed, couldn't find problem) The bushing has tabs that are bend over onto the cross member to hold it in. When these tabs unbend (from power shifts and old age,yours) it allows the bushing to pull part way out of the member, then when you let off the gas it snaps back in place, that's the clunk. Mine was a early build #618 and the bushings had only two ests of tabs 180 degrees apart that didn't hold for long.(POWER SHIFTS) The car (that I still have) is a FI, metellic brake,no radio convert. Bob

Follow up question...

Would a problem with those cross member bushings cause a thumping sound when you hit a bump??? I replaced the rear in my 1963 last winter and had to remove that member... also had to loosen it again a couple of months back to replace that front bracket (elongated holes!!). Since that time I have been getting a "thump", right rear, when I drive over a rough surface... almost sounds like an exhaust pipe hitting somewhere but I can see no evidence of that...

Thanks!
Joel

[John H.]

Re: 63 Rear Suspension Moves On Deceleration

On deceleration, the rear end of the car seems to move to the right. I've looked at the half shafts and they seem to be fine, at least nothing there seems to be lose. Drive shaft also seems to be fine...nothing lose. I do hear a clunk when I let off the gas which seems to be concurrent with swaying motion of the car. Could it be the 3rd member? Thanks for your help.
Dan K.

Dan -

The apparent movement of the rear of the car to the right is usually the result of either the rear toe-in being way out of spec, or (as Joe noted) you've lost some of the toe-in shim pack at the front of a rear trailing arm, and the front of the arm is moving laterally on the pivot bolt under accel/decel load, "steering" a rear wheel. Check for lost shims.

[Bill M.]

Re: 63 Rear Suspension Moves On Deceleration

It's a long shot, but check the bracket on the frame that supports the differential crossmember. That bracket on my brother's '67 broke loose and had to be repaired.

[Daniel K.]

Re: 63 Rear Suspension Moves On Deceleration

Thank you all for helping out with your experiences and advice. I did look at the right side trailing arm and there are missing shims to the outside right. This, more than likely, is the issue. However, I think it will be prudent to check all the other fasteners associated with the rear suspension as many of you have indicated. Thanks again for all your help.

On replacing these shims, will the trailing arms need to be re-aligned?

[Chuck R.]

Re: 63 Rear Suspension Moves On Deceleration

For sure on your problem trailing arm side Dan.

While it's in the shop, and in the air, double checking the other side isn't going to cost you that much more to gain the peace of mind knowing it's OK.

Chuck

[Daniel K.]

Re: 63 Rear Suspension Moves On Deceleration

Thank you Chuck.

That is the plan. Both sides will be evaluated and brought up to specifications.

Thanks for your reply.

[Bob B.]

Re: 63 Rear Suspension Moves On Deceleration

Bob, sounds like a very special Corvette! Can you please post pictures?

Thanks!

Steve

Steve sorry it took me awhile to get back with the photos, first I had to find some and then figure out how to send them. Bob