Ok it all started like this....I always had a weird vibrations in my 88 firebird when i was doing over 110 miles per hour. They only happened at these hight speeds so i disregarded them because my car was totally stock. Then i added springs, poly bushings, adjustable panhard rod, adjustable shocks, and control arms. These upgrades made no difference with relations to the vibration at high speed so i continiued to disgregard them. Next I put on a Jegster hd racing touque arm (the one that bolts to the driveshaft tunnel). And the vibrations got horrible at all speeds. I cannot approach 85 without the car vibrating so bad i am fearing losing parts. At 35-45 the vibes are even bad. So i replaced the u joints thinking they were the culprit but, no good. The only other thing i can think of is a bent driveshaft. The vibration is so rapid so i know it is not the tires being unbalanced. The tires would have a longer wavelength. The vibe reminds me of holding a vibrator...lol. any help would would be appreciated.

 

Yep, it's the driveshaft. It may just be out of balance, and getting the 1LE d-shaft may fix the problem. 4th-gens from '93-97 had the same problem, and GM had actually issued a TSB to have the dealer replace the stock d-shaft with the third-gen 1LE d-shaft. You could also either try having your stock shaft re-balanced or get an aftermarket steel or aluminum d-shaft.

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Greg Westphal
'87 IROC 305TPI/A4

 

I am having a similar problem. How much is an aluminium drive shaft?

 

I've seen some guys on this list sell the 1LE driveshaft for around $150. You might be able to find one in a local junkyard, but chances are it's already been taken. The 4th-gen LS1 driveshaft ('98+ years) is 3" or 3.5" and aluminum, quite a bit stronger than the stock steel or 1LE d-shafts, but they'll still break if you're putting out 350+ horsepower and using slicks. You can get the LS1 d-shaft from Dal at VanDevere Olds for about $230.

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Greg Westphal
'87 IROC 305TPI/A4