00 WS6 vibration issue

[tawally]

Small vibration problem that seems to be comming from the rear of the car. The tires are new and it's not a wheel bearing. I just rebalanced all the tires. The vibration is from 75 mph+. It is very noticable in 6th gear under full load. If I put the car in neutral and rev the vibration seems to go away. I checked the u-joints and they seem ok as well. The car has 3.73s and are slightly noisey, I am using mobil 1 synthetic gear oil with the additive. I was wondering if the driveshaft could be off balanced or torqued. The car has 42K miles on it and has been to the track a few times. Also, the rear pinion seal is leaking, it's the fourth one and it never seems to stop. Has a T/A diff cover. Any help would be greatly appreciated.

Thank you,
Walter

[Mr. Luos]

What kind of balance was done on the rear tires??

It very easily could be the driveshaft out of balance as well.
Did the problem begin with the gear install?? That could be the problem as well.

[wrightz28]

Originally Posted by Mr. Luos

It very easily could be the driveshaft out of balance as well..

Agreed there.

Also, I 'm not sure if it's so much an issue with 4th gen rear ends, but 3rd gen rear ends had pretty much axles made out of butter it seemed when it came to getting a bit sideways and even tapping a curb. They would bend extremely easy.

[tawally]

The problem did not start untill 20,000+ miles after the gear install. The tires were balanced on a high speed balancer.