NJ-xj

i know when you do a lift kit your supposed to drop the t-case. the guy before me put on the lift, its a RE 5.5. i hear a vibration from the back and i think it may be drive angles. i dont see any spacers between the cross member and where it mounts but im not sure its the OEM cross member. any help?

xjcrazy

Well if he used the spacers it would be really easy to see that it was dropped but if he used a thinner cross member that would be a little harder to tell. If you would post a picture of the cross member that is currently on your xj, then one of us could go outside look under our jeeps and tell you if it's stock or not. Your one pic away from having your question answered.

Donnie_K

I'd say if it's not dropped, don't drop it, get an SYE.

MasterShakeXJ

you're not "supposed to" drop the tcase...some just use it as a band-aid fix until they can do an SYE.

i think if it has a drop it should be pretty noticeable.

NJ-xj

well im pretty sure i have a sye. if thats what this is

SeriousOffroad

Yes, that's a slip yoke eliminator.

NJ-xj

ok thanks, but the only reason i think it still needs to be dropped is because i get alot of vibration from the rear end. because i know if the drive angles are bad from not dropping it causes vibration, is tha what the sye eliminates? bad drive angles?

SeriousOffroad

No, an SYE eliminates the slip yoke and nothing more. Driveline angles are a function of the leaf spring perches. A rig equipped with an SYE should have the axle pion pointing directly at the t-case.

Vibes can be caused by:
bad u-joints
driveshaft not balanced
driveshaft and yoke out of phase
improper pinion angle,
bent axle shaft(s)
bent drive shaft
severly worn leafspring bushings

NJ-xj

ok well the vibration starts at like 10-17 mph and vibrates under acceleration and heavy breaking, i know its not brakes or tires. it like a humming like really loud bfg's but only under accel. very weird. where would be a smart place to start?

Metmknice

I would say check your u-joints and pinion angle. and replace joints/shim as necessary.

BlueXJ

Shim the rear so the pinion points toward the transfer case. or the angle of the driveshaft at the pinion is near 0 degrees.

BenBru23

Axle shims maybe?

Mud_Pirate

hey, i was just reading the thread and i realized you said that pic is a SYE. that is whats on my unit, but i didnt think it was a SYE. if so thats sweet the PO put it in i guess.