First off ever since ive had the car ive had this issue with the car where its had bad hwy speed vibrations. Ive replaced both axles and replaced steel ds for ls1 alum ds. This fixed the vibration alot as it would vibrate constantly soon as i hit 60mph and got worse the it got. It still did vibrate a bit once it hit 75-80mph. Ive had my wheels balanced and they should be fine. Now its to the point now where it hits about 55mph and up it will get a pulsing vibration not a constant one. I have full umi outback with a custom bmr track pack style torque arm. What would cause this weird pulsing vibration?

Ideas?

 

It could be the pinion shaft. Mine was so bad I couldn't go over 65mph w/out my teeth rattling.

 

Mine is doing the same but i think i need to clock my driveshaft. Im not sure if that would work with the ls1 ds.