Some friends and I put in a new Moser 12 bolt and have been having a horrible vibration from 40-50mph and from 75-95. My friend and I have also tried all kinds of different things to fix that and nothing has helped. Pinion angle, tires, and tranny mount. Now, the driveshaft had to be shortened about 3/4 of an inch and we also tried flipping the around but it did not help. I do not have an adjustable panhard bar and have noticed the rear end now sits towards the drivers side b/c the torque arm hits the tunnel a littile bit. My next is to buy and adjustable one to fix that.
I have seen people with about the same problem and they just bought new drive shafts and it fixed the problem. Right now, I really don't want to drop like $400 on one if I do not have too.

I do also have a motor vibration I cannot figure out. It started at the end of last year before the 12 bolt. I posted about it in the LT1 tech forum, but I do not think that they are related unless maybe it is something with the clutch. The motor vibration feels like it is unbalanced now.

Any help would be greatly appreciated.

Thanks!
Josh

 

About the motor vibration - check your harmonic balancer to see if the outer ring has slipped in reference to the inner ring. My old LT1 Caprice had that problem. Bought a new balancer and it went away.

 

You can try and have your driveshaft balanced again. Some shops who do driveshaft modifications only do a low-speed balance (~3K rpms); Try to find a place that will do a high-speed balance closer to 5-6K; this might help your problem.

I had a similar problem, but I went right to the $400 guarenteed not to break for life Denny's Nitrous Ready.