Surewhynot

iTrader: (1)

Car in question is a 1985 olds cutlass with a 5.3 tremec magnum and 4.10 7.5 ten bolt and new 3.5 steel pst driveshaft. So last summer was the first summer with the new trans setup. I had a vibration at about 75. It wasn't steady, more of a surging vibration, so I figured it was u joint angles. The trans is 3 degrees down (pointing the slip yoke at the ground). The pinion is 5 degrees up (pointing at floor board) driveshaft angle is 5 degrees sloping down toward the rear. I even downloaded the tremec angle app. Could this be a motor mount issue? Any other ideas?

Crf450r420

iTrader: (1)

The front of your trans is pointing up and front of your pinion is pointing up. If they match that is the least you should have and depending on your suspension you will need to lower the front of your pinion more. I very stiff race like rod end can be matching. Energy suspension bushings would be around 3 degrees down. Rubber will be about 5 degrees down. Leaf springs would be about 7 degrees down.

So if your trans front is pointing up 3 degrees. Rod end suspension 3 degree pinion. Energy bushings 0 degree pinion. Rubber 2 degree pointing down pinion. Leaf springs 4 degree down pinion. This is a rough start and you may need more depending on how much torque you have and it turns the axle when you accel.

Surewhynot

iTrader: (1)

thank you. I have rubber housing bushings, poly frame side control arm bushings and rod ends for the lower. I will knock the pinion down to 0 and take it from there. Is 3 degrees on the trans good?

Crf450r420

iTrader: (1)

Yes your trans is fine where it is. If you drop to down to where they match, you should be vibration at speed. Might have some when you accel, so just keep dropping it a little until it doesn't vibrate at all.

Surewhynot

iTrader: (1)

great, thank you. If the weather ever breaks, I will report back