I have a bad vibration at 70 mph. I checked the wheels and tires and are ok. The vibration starts at 70 mph and does not change even when I knock it out of gear. The drive shaft does have some varience but does not look bent. Could the drive shaft be the problem? Any ideas?

 

I have the same problem on my firebird. Usually starts at 75-80 and gone by 85-90. At 50k the dealer fixed my T5 under warranty and it went away. Then it returned and very noticable at 100k miles.

At 140K I've decided to do a major overhall on the drivetrain. My front bearing was shot on my T5. The front seal was also bad and leaked fluid into my clutch housing. I just had my T5 rebuilt. Also replaced shocks, rear control arms and panhard bar.

My vibration really shakes the shifter, i.e. front of the transmission, and not from the rear end. It really didn't matter what gear, 5th or 4th I was in. If this is the same vibration you experience, them its problemly caused by the front bearing in the T5. When you remove the transmission, if there is alot of side to side play on the front shaft, then you have a problem.

In two weeks my car should be back together, I'll let you know if the vibration is gone. Otherwise I am just as lost as everyone else...

 

my car vibrates a little above 80mph and i have changed shocks struts springs all new poly bushings on both swaybars. idk what the problem is but it isnt as bad as what yours sounds like. note i havent drove the car above 70mph w/ the new struts on so that might have been the problem i dont know yet.

 

Im Having the same problem on my 87 Iroc. The 70 mph vibration got worse when I changed my rims so I dont think its a wheel balance issue. But in any case Im going to re- balance my wheels and change wheel bearings and see what happens. Ive got a rebuilt 700r4 out of a vette with a new converter. Im also currently swaping my 273 rear for another rear with 373 gears in it. I wondering If I should just swap the u joint or drive shaft while im at it? They seem ok but I really want this problem solved. One thing Im not to sure of is the suspention set up (tork arm ect.) Im also wondering if the problem is in there? At any rate Ill find it sooner or later and post again. Does anyone else have any suggestions? for us?

 

I _had_ a vibration.....

I did everything all of you are talking about....new tires, new rims, new struts, had the driveshaft & rear axle inspected....had all suspension bushings checked, checked all front end parts.. the entire suspension. everything was fine.... or so they said.

However, the Vibration was still there from ~65- 90mph. it felt like it was from the middle of the car or the read end....it actually had a sound at 70-80mph that drowned out the radio....like something was really just not right. I honestly figured it was the rear axle bearings or pinion personally.


How i fixed it......


It was the transmission mount on the cross member. mine was torn in half.
I went in for a routine transmission service and when they dropped the pan, they said the rear mount was broken and should be replaced. So i had it replaced right there and BOOM.... no more vibration- nmo more noise. The sound is gone and things are smooth as silk again.

I lived with this issue for over 5 years.... never once did it cross my mind that a 6cyl would break a tranny mount. I dont think i broke it, i just think maybe the old age got to it and that was that.