vibration issues with drop

[gmclarry]

Doing a search didn't help so I'm asking a direct question which I hope will address the problem.
2011 GMC ex-cab, short box
McGaughys 2-4 drop, spindles, rear axle flip kit and shackles.

Problem is a slight driveline vibration ranging from 50-60mph.
Is there a product or proceedure that can correct this?

Thanks for your help!

[kdhs10]

Your pinion angles could be slightly off, try checking with an angle finder if you haven't already.

[Tukin_24s]

What wheel/tire combo are you running?
Does the vibration happen all the time at those speeds or is it on a specific road/area?
My truck will do the same thing but its only due to the road im on.
That kit should have rear hangers on it as well, if you are running the flip kit & short shackles alone you are at a 5" drop

[gmclarry]

Tukin........stock wheel tire combo, any road surface, 50-60mph under moderate to heavy acceleration.
Maybe rear axle shims will solve the problem.

[BHB]

Carrier bearing spacer(s)