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Hey all,
my 79 corvette has a clunk when shifting into reverse and then into drove from a stop. It also has a clunk when you let off the gas quickly and also when you go from decelerating to accelerating. I have replaced the "doughnut" on the rear end. Its got a turbo 350 transmission and a 327. I replaced the u-joints with the correct spicer solid u-joints about 4 months ago. I have changed and added the correct rear end fluid and additive regularly.
The rear end looks like it was rebuilt by the previous owner and it also has a new rear spring. When driving at about 65 in third gear the rpms are about 3500. Could it be incorrect backlash when setting up the differential?
Has anyone experienced this before?
thanks,
Wesley
Could be, I'm no expert on that subject. Have you checked the transmission mount?
I have not. I have a box of new bushings for the whole car that I've slowly been working with when removing and restoring parts. I will jack it up and check that tomorrow. It being lowered 5-6 inches doesn't quite help looking underneath the car. lol.
Hi, Had this on my car, when cold and put in reverse, found the rear end was lose,wheel bearings and trail arm bushes.It might look like its been done but there is no harm in checking!
As Terry said check for movement in wheel bearings and trail arm bushesDave NZ
Sounds like a snubber bushing to me....But they may be what your are calling the doughnut....? Could be bad trailing arm bushings, if the they are bad the rear end will seem to have a mind of it's own when getting on the gas....Almost like it's trying to fishtail.
Hi Wesley,
Welcome!
First Posts!!!!
Yes the bearings in the trailing arms are replaceable but require some skill and specialized tools to do so.
Many folks send their trailing arms to one of the companies that do that work on a regular basis to have it done.
It's a bit costly, but once diagnosed, NOT a problem that can be ignored for very long.
Regards,
Alan
I just took a little time and jacked up the rear end of the car. The only movement in the tires is when I grabbed them at 12 and 6 and rocked them back and fourth. I can't feel or see any movement in the hubs but I can see the trailing arm rocking back and fourth a good bit in the "box" in the frame. I can also see the halfshaft yolks being pushed in and out of the differential between 3/8" and 1/2". Everything else seems tight and good. I am very mechanically inclined and can rebuild or set up anything that I'd need to. I've done frame off restorations on a 78 and an 84 k10. No shop has ever touched my vehicles as I like to learn how to do it myself. I've done everything from full paint jobs to rebuilding motors.
I just need some insight as I am still learning about both my corvettes and how they're set up.
Thank you you guys for being so helpful in this process.
Could the bushings in the trailing arms be causing the back and fourth movement?
Hi Wesley,
I believe it's the amount of shims used or not used that would allow the side to side movement.
The 71 Chassis Service Manual suggests using the shims between the control arm and inner side of the frame pocket to set the "toe-in".
Once that is achieved the other side of the control arm is to be filled with shims.
It further cautions to not use undue "force" on the shims on the outer side of control arm to fill the gap. Undue force can lead to a change in the toe setting.
I think you have found the problem....Worn out trailing arm bushings. I just went thru this project myself and like you I'm a do it yourself kind of guy. It turned out nice and I have had no issues.
This ain't a job that can be done with just a set of hand tools.
If your bolts are rusted to the trailing arms at the frame don't even bother trying any other sawzall blade...Just get one of these.
I just took a little time and jacked up the rear end of the car. The only movement in the tires is when I grabbed them at 12 and 6 and rocked them back and fourth. I can't feel or see any movement in the hubs but I can see the trailing arm rocking back and fourth a good bit in the "box" in the frame. I can also see the halfshaft yolks being pushed in and out of the differential between 3/8" and 1/2". Everything else seems tight and good. I am very mechanically inclined and can rebuild or set up anything that I'd need to. I've done frame off restorations on a 78 and an 84 k10. No shop has ever touched my vehicles as I like to learn how to do it myself. I've done everything from full paint jobs to rebuilding motors.
I just need some insight as I am still learning about both my corvettes and how they're set up.
Thank you you guys for being so helpful in this process.
Could the bushings in the trailing arms be causing the back and fourth movement?
Im sure someone will chime in about having 1/2" yoke in/out play. In other threads people are concerned with 1/8" of play, You have .500 thousandths
Good point about checking the yoke end play....make sure to check it with a dial indicator....It's amazing how 1/8" can feel like a mile. Also even if the end play is OK it's still a good time to drop the differential if any of the seals are leaking and paint it before putting it back in.
drivetrain clunk
Dave NZ
