vibration

I've got a 79 vette with an automatic. It has a mild vibration starting at 40 mph. When I drop it in nuetral it stops. I've checked wheel bearings and u-joints, all seem good. Tranny slip yoke has a little slop. Could this be my vib??

Thanks
Gary

The slip yoke is possible. But a j-joint with no slop can be dry, and could still be the problem. If that's the case it will have slop sooner or later. Best to fix before that happens if that's the case. Don't forget to check the rear shaft joints.
You could also have a weak motor or transmission mount.
Another possibility is and exhaust components misaligned or weak hanger.

Gary,

One simple possible fix..... My exhaust pipe got up against the cross member where it passes through, drove me nuts till I found it. I added a flex hanger to pull it away from the frame... Smooth as silk...... well..... as smooth as a '78 Vette can get......

Dave

I had the same vibration, all seemed ok 'till I removed the driveshft. Best to remove and check for dry joints and if the lock rings are seated properly.

kstyer said: The slip yoke is possible. But a U-joint with no slop can be dry, and could still be the problem. If that's the case it will have slop sooner or later.

I wholeheartedly agree... i just replaced all four joints on my truck a few weeks ago... they had no play. but i had a vibration that started about 40 or so.

the bearings in most of the joints were solid rust... when i pulled them apart they pratically disintegrated.. and yet there was no play...

if you do not know for certain that the joints have been replaced in the last five years.. then do it.

u-joints are definitely on my "if in doubt, throw it out" list. they are going to go out sometime.. and if you ever seen what happens when you drop the front of a drive shaft at 70 mph... youll understand..