Ok well I installed a T56 transmission in my 88 IROC and now have vibration at speeds over 70mph. The crossmember, driveshaft, torquearm (adjustable), Transmission with adapter all from Spohn.net. All I can think of is the torque arm is adjusted for the wrong pinion angle. Any thoughts on what could cause the vibration.

 

Driveshaft or Flywheel.... Is it knocking?

 

Sounds like you know whats going on.

Somehow the pinion angle was slightly altered when you installed the new torque arm. That's why Steve includes the free angle finder.

 

I swapped a T5 and a 350 SB into my 87 from a 2.8 and T5 and I get mad shakes in the shifter anywhere over 80kph. It gets sick bad when shifted into 5th too, same thing?? Torque arm angle?? It has been baffling me for months, and I am scared to take it up past that speed. I reused the stock torque arm, so I thought nothing would change.
Driveshaft and rear end are both stock.
Any thoughts??