Mike.

iTrader: (1)

To start, I have a 97 Firebird with an lt1 and t56 trans.

I've been chasing a high speed vibration for months now, and I'm starting to run out of ideas.

Tires have been rotated and balanced, the car has been aligned, I installed new ujoints in the driveshaft, checked exhaust for clearance everywhere.

Above 80 mph the car shakes like crazy. Clutch in or out, 4th, 5th, 6th, it shakes doing it all. I even ran it up to 80 while the car was in the air on a lift and it shook.

The only thing I haven't looked into is a low howl, like a tire noise, coming from the right rear of the car. Maybe an axle bearing or something? But I don't think that would cause what I'm getting. The car shakes BAD.

Anyone else have something like this happen? Most of the threads I've found searching they never solve the problem.

Catmaigne

iTrader: (6)

I had some nasty vibrations from my stock steel driveshaft. Going to 4.10 gears definitely didn't help. Felt like the car was going to rattle itself to pieces at 70+. Switched to the 1LE aluminum shaft and the vibes went away.

ThoR294

iTrader: (6)

if its all speeds.. its nothing like my vibration, which only happens in neutral.

did you balance the tires? Were they actually roadforced and checked to see if they were bent?

if its at those speeds regardless of what gear or clutch position, I have a feeling its in the rear. Axle/bent rim

do you feel it in the wheel or in yer butt?

BALLSS

you have a "cue" being a noise....I would check for a bad axle bearing...which will score a axle (read can cut it in half) and in the process vibrate considerably. remove tire and see if you have movement in the axle

Mike.

iTrader: (1)

Tried to get a video for you guys. This is doing 90 on the lift. It's a lot worse than it seems. I pulled the diff cover and everything seemed okay. My torque arm has a very small bend in it, and I'm using a poly torque arm mount. I wonder if that could be a possible cause?

The mechanic I brought it to said I have a miss, almost like a dead cylinder?

SS RRR

iTrader: (2)

I don't remember reading that. If that is the case then it's quite possible it is a pinion depth/backlash issue. Usually symptoms of a depth issue is the rear will make the most noise when the driveline unloads. Not sure if you've already done this, but it'd be a good idea to check the pinion nut just to make sure it's not extremely loose.

ThoR294

iTrader: (6)

haha its all over my thread!!!!

I will, I am actually going to pull the cover off anyway to see if everything is ok in my rear I bought. I will check

ThoR294

iTrader: (6)

Did you check the axles for a bend? Wheels?

SS RRR

iTrader: (2)

I'm a speed reader. I just miss 90% of what I see...

Firehawk197

I'm 99% sure your problem is a drive shaft as I have just solved this problem myself! I tried everything until I received a new drive shaft that made everything smooth again. But it would vibrate things loose on the car and the shifter would vibrate so bad it was uncomfortable to hold and just sounded like it was vibrating the tranny to pieces.

SS RRR

iTrader: (2)

GM had a TSB back in the early/mid 90's regarding customers who complain of vibration. The solution was to change it out with the aluminum 1LE driveshaft, free of charge. Unfortunately the TSB was only for cars still under warranty.
This was all the rage back then. Many threads about vibration and the stock driveshaft was to blame. I had the same thing and had to fight the service manager for at least an hour before he gave in, and that was me having the TSB number and printout of the description in hand. The idiot said the only reason why I was able to have this done free of charge was because my car was an SS.

great421

iTrader: (1)

If you have not tried these two things;

1. Have your driveshaft straightened and balanced
2. Have your tires check not only for balance (as you've indicated), but also for being out of round - this can be resolved by tire shaving. BTW - very few places actually have the equipment to perform this task anymore.

If you put a gun to my head, I'd say it's your driveshaft.

(FYI - I get my 3" dia Aluminum ds straightened and balanced about every 2 years, then the driveline is smooth as butter.)

Good luck!

Catmaigne

iTrader: (6)

Get the driveshaft. They're pretty cheap and if your vibration isn't cured then sell it and get your money back. I sold mine for $100 a few weeks ago.

Also, measure your pinion angle. That can jack things up at high speed.