hello i got my 71 cutlass s on the road a few days ago and i get a vibration at 60mph which tends to lessen alittle the faster i go and is not evident at lower speeds heres what ive done so far.

everyone said u joint or drive shaft i had the wheels balanced again first took the drive shaft out had a new one made with another new set of u joints i used the old yoke put it in and it does the same thing exactly. something would be different if it was the drive shaft i would think .the yoke is the only common part ive reused and it seemed fine before i did the frame off i have new or rebuilt everthying under the car and cant figure this out i put the car on jackstands and took the rear wheels off and the drums put the car in drive and ran it up to 60mph same vibration as when goin down the road. i dont think its the motor because if i put it n while coasting at speed it still does it the rear of the shaft looks to be wobbling more than the front the rearend was just rebuilt as was the tranny sorry so long any ideas?

 

Did you get a front end alignment. I had a problem with a fwd car with the rear end out of alignment because of a accident.

 

ya front is good car feels great till 60mph it does the same thing on jack stands without the wheels on it

 

Flexplate or torque convertor. Maybe both. It makes it feel it's from the rear or part way up. JMHO. Been through it.

 

OEM, or aftermarket wheels? I had an aftermarket wheel with quite a bit of runout that caused a a lot of vibration. Also, have you tried taking the trans out of gear to see if you still had the vib".
Let us know..

 

maybe the flex plate is used torque converter is new when coasting in n it still does it

 

after market ion wheels but like i said it does it without wheels on jack stands

 

Did you make sure the rear of the trans was exactly centered on the frame before tightening it down when you did the frame off ? The ends of the crossmember are a bit slotted. and it may be a little off center. Just a thought. I just installed my trans during a frame off and I had to center the trans up before tightening down the engine mounts and trans crossmember.

 

Will the vibration only happen at MPH , or is it engine RPM related ? Try to manually shift the trans.and run up the engine speed.(to see if it's there at 60 in 2nd gear) You also might try to unbolt the converter and push it away from the flex plate to eliminate a possible torque converter issue.

 

i will check and make sure the tranny is centered i did let the car coast out of gear down hill and it still did it. just reving the motor doesnt do it. the guy that did the rearend said it could be angles of the rear and the tranny what fun that will be to check all my control arms are stock with new bushings. he said the tranny mount might be the wrong height it just seems too be a thousand things that it could be. i tried to do everything new so i wouldnt have these problems

 

well guys i checked the tranny it is centered. i loosened the rear control arms. indicated the axles and made a fixture at work to indicate the rearend yoke it was about .040-.050 out axles were .003 & .010 i threw everything back together and the vibration is totally gone so you got me i have no clue what changed other than loosening the control arms an then retightening them oh well better to be lucky than good thanks for all the info! now the brakes!

 

I've seen driveline vibrations cause good men to go nuts.