I own a 95 Z-28 6-spd ragtop that needed rear carrier bearings because they were getting noisy. I had a reputable shop replace all the rear bearings & seals & while they were at it I decided to throw a set of 4:10s in to fun things up a bit. Since getting the car back I too have the imfamous vibration that numerous of you have posted about at aprox 75mph - 95mph, present with power on, off,clutch in, neutral whatever you do vibration is present at this speed range.

So far I have had original drive shaft balanced 2 times. Checked end trans bearing. Replaced trans mount. Took the advice of several topics I read here & had a new 3" steel drive shaft custom made. Vibration is still there, the only real change I have noticed with the new driveshaft is that I can power through the vibration now, if I keep my foot into it the vibration goes away & its smooth as silk once past the 75-90 mph. I have taken it back to the shop that did the original gear swap & bearing replacement. They have opened the rear cover & everything looks picture perfect, perfect fluid, perfect bearings, no marks on the ring gear - visually perfect. They have refilled diff & ran with car on jack stands and 1 by 1 removed the wheels, then rotors, pulled the axles & the vibration is still there. They have also tried my old pinion just in case the new one was out & same %$!!&*^ vibration.

Everyone is stumped on this one, and I definately am not getting screwed over by an incompetant shop. I work in a large auto dealer service department and the shop that has done the work are straight up good guys who we do business with. This is just one of those stupid mysteries that should have not taken this much effort to be comming up with the same *%$%$#@!@# vibration, this should have been fixed with the new drive shaft. So if any of you gear heads out there have had a vibration this tough & beat it what did you find the problem to be. Any help would be greatly appreciated as I am fairly frusterated now.

Thanks
Krusty

 

is the shake in the car or the steering wheel? if in the steering wheel it could be front wheel bearings or ball joints.

 

Vibration is definately from rear of the car. Front end is perfect.

 

What tranny mount are you running? Are your rear coil springs the originals if so they are probably sagging causing you pinion angle to be off.

 

A lot of people tried to balance the stock DS's and failed to eliminate the vibration. I think it may be a case of the DS reaching its "critical speed" and producing harmonic vibrations, not imbalance vibrations. An aluminum DS from a 1LE or an LS1 would be worth a try.