Vibrations only at certain speeds is a result of an inbalance. Be it in the driveshaft, or the wheels. As stated above.. your driveline angle is f'd. Also since that is f'd change your ujoints front and rear and get angle right.. with a sye your pinion should be pointed right at the output.

 

I agree with this, So what i would do is change your shims to maybe 4-6 degrees. and if that doesn't work, if its a H&T, check to make sure he drilled the hole center

 

pull your shims out or go to another "driveline specialist". ...also how can the hole being drilled off center cause a vibration?. the splines center the yoke on the shaft so i dont see how it could cause a vibration.the center bolt retains the yoke on the shaft...i am confused on that one
cameron

 

i have a rusty's 4.5 with 2" bb on top i have a 6* shim and stock drive shaft(extended yoke no sye) and no vibes from mine i have to agree with others the 8*shim is to much for that size lift it has the drive angle to steep making you drive shaft vibe at highway speeds reduce the shim and replace the u joints that should fix the vibe hope this helps

 

hmm, yeah, i guess you're right. i didn't think that far in. good point.

well, i'm not sure then. but when you lift, all the angles change, so something isn't agreeing on the new angle.
was the rear driveshaft new? maybe a u-joint could be pressed in too tight?

 

and if that doesnt work try checking the differentials in the dash lights.
On a side note, you may want to avoid parking on a hill because the "park" only locks the flywheel, not the other three wheels.


but to really help your problem..... i would take your jeep down to a tire shop and tell them to update your tires to summer air so they ride smoother.

 

5 inch lift, no T-case drop,no sye, no shims, busted motor mounts, no vibes. Sounds like you got the shaft.
Turn up the stereo and ignore it.
FYI might want to get a new track bar