Outer Limits 4x4 Board

Got a GQ shorty with 2"spring + 2"body. Car rides on 35 pedes & 31's for skates. Problem is with the 31's anything above 60km get a horrid noise from the rear, sounds very similar to the dotted lines they use on the hwy when driving over them. Could this be a result of not having gearbox packers? Only makes the noise whilst not accelarating. Car has never made this noise before, but has only ever been driven on 33's an 35's with these mods.
If it is a result of driveline vibrations what damage could be expected?

Your thoughts

I had what sounds like same prob turns out it was angle of the dangle on tail shaft, spacers should cure it on a 2'' lift.
imo cheers lou.

Rather than lower your crossmember and give you less clearance, I would install longer lower control arms that rotate your diff giving you a straight coil pearch, panhard mount and shock mount and also putting you tailshaft uni's within 5 degrees of each other. Lower control arms need to be 12mm longer for your 50mm lift to get everything back to normal.
Cheezy