I just installed a new rear end, 12 bolt with the Hotchkis upper and trailing control arms, braces, 1" lowered springs, air bags and KYB gas adjust shocks. I adjusted the upper control arms to 10.25" center to center which is the stock length. Will the 1" lowered springs change the pinion angle? I am thinking this might be the cause of the vibration. I pick up the vibration about 60 mph. The car did not have it before the swap. Also the pass side bushing in the differential housing was not driven in all the way, but it is within 1/16" from the other bushing. Could this be the cause? Judging from the set up I took out there was more than 1/8" of slop in the control arm mount points on the differential, so I doubt that is the issue. Any sugestions? If needed, can I change the length of the upper control arms to adjust the pinion angle?. BTW, I did not measure pinion angle before the swap.

TIA, Kevin

Kevin,

I can't give you an exact answer, but I was reading a thread here yesterday and someone said that when they installed taller springs in the rear it wore out their pinion bearing very quickly due to the change in pinion angle.
While I think they change was three inches higher, your one inch drop would theoretically contribute to the same sort of change, only in the other direction.

Sorry I can't help more. Haven't made any of those sorts of changes yet. Just wanted to give you some food for thought.

Ya didnt sit on your wifes toy....did ya??? :D j/k

How'd you know she had one of those, you been coming around my house when I'm at work?

my rear end was making some wierd noises too, try changing your diet. it worked for me.

OK so much for jokes, should I post this in the transmission forum? I still need to know what might be causing this and how to fix it.

Kevin

Did you change driveshafts with the swap? Did you change tires and wheels with the swap? Lowering it 1" would not cause the vibration.

You don't need to know the pinion angle before the swap. It should just be the same angle as the transmission after the swap, shouldn't it? I would check this and adjust the control arms if necessary.

The u-joints front and back need to have the proper angle to cancel vibrations, I bet your pinion is pointed up to far.

Kevin,
For what it's worth, someone had the same problem you have a while ago and they replaced both u-joints to cure the problem. I don't know if this'll help in your case but it might be worth a try... (I thought the jokes were funny...) Chris