Hey guys so I bought a 5 inch lift from super lift "I'll never buy anything from them again" so their kit came with 7.5 inch rear lift blocks for a 5 inch lift I called them and they said that is the block for that kit. But anyway I have a hell of a rear drive shaft vibration at highway speeds when I'm letting off the gas only. It makes a humming noise. Its wailing really. But anyway it screwed up my pinion angle really bad I had to put 4 degree shims and and it still didn't fix it. So then I took the blocks out and put two 3 inch blocks together to make 6 inch blocks it completely took away the vibration. So my question here is what do I have to do to take away the vibration when I have the 7.5 inch blocks on. And I don't want to lower my transfer case that's can get pretty expensive.

 

Two ways and the only two ways (in not going to tell you that running that big of a block or 3 blocks stacked like you are doing is extremely dangerous) drop the transfer case or get a custom driveshaft made.

 

Anytime the driveline angle changes, new ujoints should be installed. I had new tires installed that caused a vibration. They were slightly smaller and caused a worn ujoint to vibrate due to new angle. And wow, the superlift website is all over the place. The kit shows control arms and blocks while the description says it uses AAL and radius arms. Someone needs to be fired.