Over the last six months I have been scanning this forum for ideas on fixing my wife's '88 Vette (automatic). It had a severe vibration between 65 and 80 MPH. Based on knowlege gained in this forum, I have been replacing parts a few at a time to see what provided the biggest improvement.

It now has over 167,000 miles and I can officially declare the vibration to be gone! For those of you faced with the same vibration problem, here is a summary of what I did:

1) Replaced left rear hub. Barely reduced vibration.
2) Replaced right rear hub. Barely reduced vibration.
3) Replaced right front hub. Barely reduced vibration.
4) Replaced left front hub. Barely reduced vibration.
5) Had drive shaft fully serviced (u-joints, straightened and balanced). No noticeable improvement.
6) Replaced all four tires with new ones. Biggest improvement but some vibration remained.
7) Replaced trans tail piece (including bushing and seal). NO MORE VIBRATION!

I test drove the Vette in a secluded area up to 110 MPH. Very smooth!

Conclusion: The extreme vibration was not caused by any single part. It was an interaction between the parts that would amplify the vibration.

It cost me about $1700 (including tires) for the parts and several weekends in my garage.

I'm happy to say, I finally won the vibration battle! :yesnod:

Good luck,
Greg Sullivan

 

THanks Greg
i would've never thought of the trans tail piece :smash: :smash:

 

Changing the tail piece went fairly smooth. The trans does not have to come out. You have to remove the exhaust pipes from the engine to the rear end. Mine are not welded so they just un-bolt and drop down. Then you loosen the 4 foot driveline brace that connects between the trans tail piece and the rear end (differential). I've also heard of them referred to as "torque arms". There are two large bolts on each end. Be sure to support the trans before loosening the bolts. The trans will want to drop down without support from the brace and that will stress the motor mounts. There is no conventional transmission mount or cross brace.

Once the driveline brace is loose in front and back, you pull the drive shaft out. Once the drive shaft is out, you remove the driveline brace. This is where I ran into trouble. I could not get enough clearance to either side of the trans to be able to get the brace off of the trans. Then I took a pry bar and forced the trans to one side about 1 inch. Then the brace came straight down.

Then you un-bolt the tail piece from the trans case (4 bolts). Then it slides right off the trans shaft. Then you swap over the speedometer gear and housing. Install the new piece (with seal and bushing already in) and reverse the above procedure.

There is a large rubber ring that should be replaced.

Extension part # is 24201517 (includes rear seal and bushing). I paid $75.90 for it from Superior Chevrolet in Kansas.

The large rubber seal that goes between the trans and the extension is part number 1358899. It cost $1.15

I hope this helps.

Greg Sullivan