I have a Moser 12 bolt w/4.10 gears and have about 2,000 miles on the rear end set-up. Don't know if this is normal or what but when I shift into 4th gear at high speeds the car stops pulling and a weird, small vibration starts coming from the rear of the car. I think. I know that really doesn't describe it all that well but its kinda hard to explain. The rearend was set-up by moser if that helps any. Any information would be great. Might not even be the rear-end but for a novice mechanic like myself its a starting point.
The first thing I recommend is to check the four torque arm bolts that attach the torque arm to the rearend. The top two have a habit of working loose, even when loctite has been used during assembly. Bob