real82it

So, similar story to many regarding new 9inch and vibration:

Bought and installed a Moser 9 inch in 95 Firebird
Bought and installed a Moser adjustable torque arm
Adjusted to -3 degrees as suggested
Got annoying vibration from 50mph and above - got really bad above 80mph

Adjusted, and re-adjusted, and re-adjusted, and re-adjusted the torque arm with no success.

I should mention that I had an aftermarket "stock" replacement PST aluminum driveshaft. Measuring the length determined that the driveshaft was appx 1/2 inch shorter than stock.

Then I determined that the Moser rear end caused my driveshaft to stick out of my transmission (A4) appx 1 inch more than the stock differential.

So, I went and priced getting my driveshaft lengthened 1.5 inches - $350.00 OUCH.

I then had the driveshaft shop put a new yolk on the driveshaft that was appx 1.5 inches longer than the one that was on the PST driveshaft. ($90.00......much better)

BINGO. No more vibration. (I have the torque arm set up at -3 degrees).

wrd1972

iTrader: (12)

A search would have gotten you fixed even quicker. This has been beat to death.
BTW set your angle to 1.5-2 negative pinion angle.

EPP

iTrader: (22)

A stock replacement PST driveshaft should be the same length as the stock driveshaft. The stock length is used for the 10 bolt and 12 bolt rears. The nine inch rears need a one inch longer driveshaft, which would be 45.25 as measured by using the x dimension on this chart. Bob