I have a 97Z M6 that starts vibrating at 70 mph and gets worse the faster you go. the vibration is also worse with weight in the car(4 people,luggage). i have put on a ls1 ds, new u-joints, tires rotated and balanced multiple times at different shops. i don't know what is next any suggestions appreciated. also it doesn't matter 5th or 6th gear the vibration is the same.

 

Was it a brand new LS1 driveshaft or a used one? I put a POS used LS1 driveshaft in my car and it still vibrates. I should have spent a little extra money and got a new one.

 

it was a used one. it wasn't beat up or anything though. did you replace yours with a new one? is it possible to balance the ls1 shafts?

 

It can be balanced, it's just finding a shop to do a "high-speed" balance.

The shop I used to use only did 3600rpm balancing, you need to find a place that can take it to at least 6K rpms if not more.

It honestly sounds like a DS issue, and see if you can find a shop to do the HS balance. I know you can send it to Denny's, but he's got a 2 week backup on balancing right now. He can get a LS1 shaft to 6-7K rpms balanced.

There are other things that can cause your issue:

Pinion Angle improperly set
Bad bearings in the Pinion
Bad transmission output bushing

Either of the last 2 can be detected by trying to mode the DS up/down/left/right and seeing if it moves a way it shouldn't.



I've been fighting a problem like this for over 18 months, I finally said F-it and just ordered a new DS from Denny's. I tried a LS1 shaft and it didn't do squat, even after having it balanced, although I believe part of it was the shop that balanced it (I have heard some horror stories lately about them balancing shafts; it wasn't denny's who balanced them, it was another local place)