Recently swapped out my '88 D30 with bad pinion bearings for a good '96 HP30 with solid bearings. When I swapped the axle I also put in taller coils to level the Jeep and put in new upper arms to set the caster correct. Before I had a small vibration from the rear driveshaft from the c8.25 swap and no SYE at 4"s of lift but nothing bad, old D30 pinion bearings were the worst. Now i have a constant vibration since the swap. I removed the front drive shaft and noticed no difference, also replaced a bad rear shaft u-joint. The passenger side hub has a very small amount of play in it, ball joints on both sides seem solid. Can that hair of play be the issue? U joints don't seem to be greaseable but i'm not getting any binding while turning. I swapped covers and the insides look pristine as well. I replaced the pads but left the rotors, stops quick too. Also the whole Jeep decelerates quickly when letting off the gas like slightly pressing on the brake. So i'm thinking it's either A) Bad Hubs, B) Brake Rotors are too rusty, or C) Leveled height has caused the rear driveline angle to be too steep and causing the vibration. Would like to hear everyone's thoughts and ideas. Thought the swap would fix all that, but at least it doesn't jerk at the pinion anymore when braking.

 

At 4" of lift you need and SYE

 

I would pick option "C". I agree, an SYE may be in order.

 

Thanks guys, that's what I figured since the front is higher now, just wanted to get another opinion on it.