this may be a stupid question but its driving me nuts. I recently put on lowering shackles and ever since ther is a vibration at about 40-70 mph, has any one heard of this with a 2inch lowering shackle? would my pinion angle be off? from what i've read on this fourm a shim is not normaly needed on just 2". by the way the truck is a 2000 ecsb Z71.

 

Seems like 2" shackles alone won't usually cause a vibration, but anything's possible. Since the vibration started after the shackle install, I'd be looking toward a pinion angle problem.

 

being a Z71 is it 4x4? if so, did u take out the lift blocks as well?
I would agree with Budhayes that since it happened after that u may need to shim it

 

thanks for the resonses so if i put in shims how do they face? thin end pointing twords the back and thicker end twords the front of the truck or is it vise versa?