If I am doing say 90 and I let off the gas, I get a vibration. I am pretty sure that it is there in all the gears, but it is noticable in 6th. It also feels like its vibrating inbetween 5th and 6th, during the shift. The car also has a good vibration at high speeds, almost enough to keep me from going very fast.

I would be quick to say driveshaft, but I have flipped it and while it got better it did not fix it obviously. Not to mention that it was fine before I did the motor/6spd/rear end swap. Since I did the motor/tranny/rear end swap at the same time, there could be multiple culprits.

What else can you guys think of. I guess it could be driveshaft or flywheel, but since it does it both clutch in and out I would be hard pressed to believe flywheel. Maybe the lower control arm relocation brackets have my pinion angle off (can that even be since I am on the stock torque arm?). My car is lowered, but still, I would think the torque arm would align everything.

Anyone got any ideas?

 

I allso have a high-speed vibration that is most likely driveshaft-related. However, unde a no-driveline-load condition I get a nasty vibration. The best example of when it happens would be coasting down a hill at freeway speeds with the cruise control on, or very slowly decelerating by only partially releasing the throttle. Basically anything that allows the driveline to have slack in it at 50+ MPH causes this vibration. Very weird.......

 

That could be kinda the same problem as I am having.