98 grand cherokee lifted 3.5 inch rear drive shaft vibrations help

[Blackzj4x4]

Hey guys any tips on how to fix this really need help

[Mr Rock]

There are a few reasons why you get driveline vibrations, but really need more info. Did it start when you lifted it or did it just start out of the blue, is it front or the rear?

If it started when you lifted it, Skibum explained it best in your welcome post,

Welcom to the forum JJ. I owned a 98 ZJ Limmited 5.2L. Miss that jeep. Your drive line vibration is most likely caused by the NP 249 T case. I have herd lifts over 2.5in cause vibrations. If you can adjust your front pinoin angle up some it will help but also look for a NP 231. Not sure on the input spline count so you will need to do some resurch on that. Good luck

if it started out of the blue look for missing weights or dents on the driveshaft or it could be a bad u-joint.

[Blackzj4x4]

Just out of the blue , it was fine for the first year and out of the blue a guy told me to do my u joints on both drive shafts and the rear one is the one making the killer vibration not the front and we are going to pull diff cover to see what's going on in there, on top of that the outer seal on the tail of the t case is leaking fluid and if you guys know anyone that knows how to pinion seal on front is leaking but pulled front to see if it was the problem but it wasn't

[DirtyJeep92]

Pinion seals are cake. Pop off the yoke pry out the old seal. Pop in new seal and re torque yoke nut. X2 with what skibum said. And also when checking the ujoints makes sure there isnt any tension on them. Block the wheels and pop in in neutral.

[kirksjeep]

Pinion seals are cake. Pop off the yoke pry out the old seal. Pop in new seal and re torque yoke nut. X2 with what skibum said. And also when checking the ujoints makes sure there isnt any tension on them. Block the wheels and pop in in neutral.

It is only easy if you can get the yoke nut off.  New England rust welds that nut in there good. 

If the T-case is leaking at the rear, there is something going on there.  SYE and new drive shaft is the right way to go.  You can get away with a T case drop, but it defeats having a lift to clear rocks because the T-case will now hang low.  A T-case drop also wont solve the leak, and the tear down to replace the seal is almost as involved as installing the SYE. 

Also check the bushings and lock nuts on your control arms.  If the bushing are worn it will throw the drive shaft angle off and comound the problem.

[Blackzj4x4]

Tcase had been dropped all ready, the bushing just checked those out everything gets retourqed all lift componts, for the sye I don't know if they make it for the 249 case, now for rust there is like 10% rust on my jeep we'll cleaned, so the bolts get wired brushed every month, and if anybody on here is going to the clean up wanna look to see and you can drive it to hear what I'm talking about