I got a 96ish grand cherokee thats my buds and when u get up to about 30mph it has a weird jerking or like a bumping comin from under the jeep. No flux n rpm so dont think its the tranny. When i get the bumping i let go of the wheel the steering doesnt move so i dont think ball joints or anything. Could it b the xfer case??

 

It's hard to say by your post. Could be the tires, brakes, wheel bearings, just can't say.