RC 6” lift CB vibration/shutter

Has anyone been able to successfully get rid of the vibration..?
I have shimmed the CB down with the provided 1.25” spacers, had really aggressive vibration from dead stop acceleration up to 10mph, it would level off then again at 18-20mph as it shifted into 2nd, then an occasional shutter at highway speeds when pushing it to passing speed… added an additional 5/16” spacer and longer 70mm mounting bolts, the shutter got better, less aggressive nearly gone when when shifting to 2nd, and did not notice at highway speeds.. added another 1/4” with plate washers, it was about the same, however did noticeably better torque transfer to rear..if that makes since.??

 

Any pics of the rear axle lift? Sometimes the angled rear blocks are installed incorrectly. Lots of complaints after RC 6” lifts for numerous reasons.

 

Yes checked the shackle blocks first, they are correctly installed, short end to the front, has just over 5/16” difference front to back, rear differential is definitely rolled up to the front…
Was considering adding more angle shim under the shackle blocks..?