I have had this vibration for a while now. It starts at 70mph and you can hear it as well. Sounds like a deep vibratins sound. Im running the PST 3.5" aluminium d/s, Spohn crossbrace mounted tq arm and moser 12 bolt. The arm is set at -2. My rear-end is setting back a little because of the relo brackets and non adjustable LCA's. Im not sure if this would cause this but its a maybe. Im also running poly motor mounts and poly tranny mount. Just thought id see what you guys think.

 

Not sure if you swapped to the poly bushings at the same time but you will get more noise with them for sure. I suspect your pinion angle is off. At 70 mph and above you start vibrating things.

 

Yea, thats got to be it. I dont remember the car doing this untill after I got the relocation brackets installed which moved the rear-end back some. I was just seeing if anyone else has had this problem so I feel better.

 

The relocation brackets should pull the housing rearward not tilt anything on a torque arm style suspension. My guess is the torque arm mount is not identically oriented to your old axle. You may need an adjustable arm.

 

I do have one.

 

I have the same problem but it starts over 80..the pinion is right on, also there is a horrible clunking and low speed turning..the rear is coming apart next week i'll see whats going to cost me more $ then