syc0path

I have a vibration from the rear end that shakes the whole car. It starts about 65mph and kinda comes and goes at speeds beyond that. I've been trying to track it down for months to no avail.

Anyway, 1 of the latest things I've tried is to measure the pinion angle. I borrowed a digital protractor and put the car on blocks as level as possible. But I don't know where to put the protractor to measure. There don't seem to be any good flat surfaces that I can hold it steady against. When I was comparing the yoke angle to the pinion angle, about the best measurement I was able to come up w/ was a difference in the 3-4* range. I know that's too much, and assuming it's accurate, what would cause a change like that? I already replaced the rear springs -- that raised the car about an inch, but it didn't seem to affect the vibration.

While I was under the car, I noticed that the torque arm was pressing upwards in the bushing -- like someone had put the car in park and shoved it backwards. Maybe that happened becuz I jacked up the front end first. Anyway, the gap at the bottom of the bushing was probably big enough to stick a pencil in. That seems like a lot of play to me... could the bushing be worn and allowing too much play for the torque arm? If so, the pinion angle would constantly be changing while I was driving, and that could cause the vibration to come and go. Has anyone ever had a torque arm bushing go bad?

Auggie

I had this problem and mine was more of a rumble and it turned out to be the lock-up torque converter. Anyhow I would change them torque arm bushings but there are bunch of things to check. U-Joints, tire balance, drive shaft streightness, control arm bushings, panhard rod and the transmission tail shaft bushing.

Auggie

syc0path

Believe me, I've checked and re-checked all of that stuff. Like I said, this has been going on for a long time.

I know other people know how to do this -- I've read lots of other posts about what measurements other people have, but none of them talk about how to measure. So how did u people do it??

syc0path

I should also mention that I recently replaced the trans mount, just in case anyone was thinking that a deteriorated trans mount might cause the difference in the pinion angle. The new mount didn't seem to help much.

91formulaSS

no, but sometimes a new mount (especially a ES poly one) will cause a pinion angle change and lead to increased vibrations. or so I've heard. TIFWIW

Lo-tec

I'm assuming you use this digital protractor tool by placing it against the driveshaft, and hit a button and it tells you the angle with respect to being level. If so, measure the d/s, remove it, and measure the flat surface of the pinion yoke with it parallel to the ground. You can stick in an old trans yoke and measure it like the rear, or measure at another level surface on the motor (the starter mounting pad is one). Then crunch the numbers. The angles should be equal and opposite (within a degree). Shim the trans as required to get it close.