Hi
My car has zero vibrations in 1st and 2nd gear to red line but has a vibration in 3rd gear from 3,500 up. When it shifts into 4th it disappears... very weird. Its actually gotten worse lately. I'm thinking that there's something wrong with the tranny. What else could it be? bad tranny mount or u-joints? Its a goodwrench 700R4 and I have only 2K left on the 3yr/50,000 mile warranty and I'm getting worried.
thanks
Craig

 

And here I thought I was the only one. Cswanson I've been plagued with this problem since I've had the car. I've gone through 3 different rear ends (they blew up for other reasons) and the problem still never went away. I would love to hear an answer to this one.

 

Better ask in the transmission board, might have better luck with an answer

 

Maybe its your driveshaft? Ive heard that steel driveshafts tend to vibrate at certain speeds, but getting an aluminum one would cure vibrations.

Im assuming u have a steel driveshaft too.

 

i put an LS1 driveshaft in my car and that virbration some people fell in 4th gear doing past 80 is gone. it didn't matter what gear i'm in


also the rear of the car wouldn't make any vibraion in one gear at a certain rpm.

 

problem solved, no more vibration... it turns out the transmition support cross-member was loose. The bolts holding it to the floor boards were all backed out about 1/8"... scary. I jacked up the tranny a little thinking my tranny mount was bad and thats when I noticed the whole bracket was loose. Guys with the same problem should check theirs.
later.

 

I'll check it tonight, any other problems it could be, I have the alum driveline?

 

what else could it be, pinion angle? trans mount seem to be fine
(anyone know the GM 1LE part number??) what else could it be, and suggestions?

 

does anyone else have a suggestion

 

Anyone

 

can anyone help or add to this problem

 

I seem to have this same problem, but I know it's not the crossmember. It only happens when in drive, and throughout the rpm range (just less noticeable at lower speeds).

I've asked about this before, and never got a response. I guess it's something about the tranny...