Okay, so my Jeep has been in the shop for 2 days. I have competant mechanics but they are having trouble diagnosing my vibration problem. The drive shaft front U joint was bad so they replaced it. They also found that the rear differential spider gear had way too much play in it so they replaced that. The mechanic took it out for a test drive (after replacing these parts) and it still vibrates at high speeds. I'm thinking it is something in the transmission like maybe the locking torque converter is chattering?
Any oppimnions here? I had the axle u joints replaced last year. It is definately a drive line vibration and not a tire or brake rotor.

 

i've had transfer cases vibrate... also drive shaft may be tweaked

 

used or new shaft

 

and to be honest your mechanic sounds like he is throwing parts at it

 

i would say drive shaft. easy way to find out it that is it is to drive around in 4x4 with both on, then take on off and take the same route, then put it back on and remove the other one. if it goes away when a certain one is off then you have a bad shaft, it it goes away when the front is off then you have a bad t-case bearing.

 

This.

 

I don't know how you'd do this...you can't drive without the rear DS and getting up to highway speed in 4x4 is super risky on pavement. That is a disaster waiting to happen.

I also can't help but wonder why, if one u-joint was bad, why wasn't the other replaced? They cost like $9 and take five minutes to swap out.

And I would not allow ANYBODY near the rear end gears without a college degree in differentials. Replacing a spider gear? What's up with that? That guy is guessing.

My advise: Do some homeboy diagnosis. Put it up on jackstands (good ones...not HF or Walmart...and make sure it's done correctly). Start the motor, put in gear and have helper run up to speed. Watch what is going on with the rear wheels. Pull the wheel/tire and brake drum and do it again. Do the same with the front while in 4x4 High range. Use your hands to see if you can feel vibrations coming from somewhere.

In the end...if you can't find the vibes, ignore them. My xj vibrates. It's 16 years old and I don't feel like throwing $1000 of parts and countless hours of time at the problem. It's just a runabout and toy 4x4.