Pinion Angle, vibration, confirm my thinking

Hi All,

I have extensively read all the threads on pinion angle settings. Experiencing a pretty good vibration at WOT towards top of second gear in a 904. Surely seams like @ drive shaft speed, not wheels and diminishes a little after shifting to 3rd. I can rev this thing to over 6K in neutral, smooth as silk.

Checked my angles last night according to all the info. At front end, Trans up .5 degrees, shaft down 1.4 degrees for a 1.9 degree difference. At the back, shaft up about 1.5 and pinion down about .5 for a 2 degree difference. Therefore currently I am setting at trans to pinion angle of about parallel, which I am thinking is not good static.

I am running Caltracs, so thinking that I have to shim for the pinion angle to rotate down another 2 to 3 degrees to compensate for torque wrap, which should put me back to parallel under hard accel.

Please confirm my thoughts....appreciate it!

Your crank/trans centerline and pinion angle are parallel. This can cause harmonics and increased u-joint wear. You are right to shim the pinion 2 degrees down.