Background: For the past 2 weeks I've been working on swapping in a T-56, Spec Stage 3, and 4.11 gears. I had the driveshaft dynamically balanced at Houston Driveshaft as well as had new Spicer U-joints put in. I also made my own swap crossmember.

Today: I finally got the car on the road, just been taking it easy around town to break in the clutch. I took it out on the highway earlier and ran it up to about 70, but at 65-68 a fairly bad vibration picks up, high frequency and definitely related to vehicle speed. I pulled it into the shop hoping it was one of the wheels out of balance, so I set it up on jack stands, removed the wheels, ran it up to 70, vibration still there. I saw another post about turning the driveshaft 180* in relation to the pinion yoke, but that didn't help either. The only thing left I can think of is either pinion angle or front yoke.

When I made the crossmember I measured the distance from the ground to the center of the output shaft of the T-5 before I removed it and did the same to the center of the T-56 output shaft. How much off at this place would it take to affect the pinion angle? 1* isn't a whole lot, especially over that distance. How much off would the pinion angle have to be to cause a vibration?

 

ok, went and got an angle finder from the hardware store.

-3*. I've heard -1 to -2 is what you want for the street. 1 degree isn't a whole lot, but would that be enough to cause the vibe?