Drivetrain Vibration Questions

[Dave Nelson]

This is why I mentioned the trans mount earlier, most of the time the damage is not noticed until replacement.

 

[COPO]

I would take it for a spin after swapping the trans mount. If you change too many things at once, you’ll never know where the problem was if it gets fixed.

 

[Glava]

I would take it for a spin after swapping the trans mount. If you change too many things at once, you’ll never know where the problem was if it gets fixed.

Oh man my bad, I had forgotten to say that the vibration was still there when I took a very long test drive. Thanks for reminding me of my goof! I have added that to my post!

 

[Glava]

Thanks again G72ZED, Checkmate and others!
So I got a new transmission mount as long as I was going to try and correct the pinion angle with shims. When I took the original one out, I realized it was collapsed. It was approximately 1/4" shorter than the new Anchor industries mount.
I installed it without any shims and the angles were 4* at tranny and 2* at the pinion. The driveshaft angle is 3*.
It seems that this is good -right?
at pinion. It seems that this is good -right?
TOOK IT FOR A LONG TEST DRIVE AND THE VIBRATION IS STILL THERE AT 70MPH -NONE IN THE STEERING WHEEL, BUT IN THE SEAT OF MY PANTS.
If so, I'm on to getting the driveshaft balance checked -right?
If so, I'm on to checking the tranny tail shaft bushing and then getting the driveshaft balance checked -right?
My bad,

View attachment 131231

I had forgotten to say that I had test driven it for quite a distance.

 

[COPO]

What a pain. My OCD would have been at the Dealers every week until fixed like I was with my stripes being on back order and then some coming in for my 78 Z28.

 

[rocket dawg]

The pinion angle theory should have some distinct symptoms. Under acceleration, the rear diff pinion would raise up ( wrap )and under braking or downshifting it would unwrap or point lower causing an angle change. This should increase or decrease vibration. Right?? Just throwing out some ideas. Is it possible the factory welded the spring perches on the rear diff way off? Its a long shot at best. Shimming the back of the trans isnt going to be a huge angle change IMO but give it a try, it inst going to break the bank and it isnt that difficult of a job.