I am having a problem with my 2001 Jeep Cherokee Sport I6 (147,000 miles). U Joints appear to be in good shape. The dealer cannot figure it out and I have been to 2 Jeep dealers. When I am going and I hit 1500 rpms, if I drive from 1500 rpms, this vibration happens... shakes the whole car. It feels almost exactly like I am going over those BUMPS ON THE EDGE OF THE ROAD to keep drivers awake. It doesn't happen if I take my foot off the gas and it falls below 1500 rpms and then accelerate. I don't know what to do? I bring my jeep in for maintenance every 3000 miles and the tires are good. It's all good according to the mechanics? Can't figure out why they don't have a clue?
Any insight would be greatly appreciated!

 

Lifted?

 

No, completely stock.

 

Lug nut torque, bearings front and/or rear, torque converter, bent drive shaft(s) are all possibilities.

Hard to tell if U-joints are good just by looking at them.

 

okay, you reach 1500 rpm from idle and while accelerating past 1500 rpm do you feel vibration... what happens when you let off the skinny pedal but are still over 1500 rpm ? still vibrate? what I'm asking is the vibration only on load or even on coast?

 

Only under load. If I coast it stops, or if I accelerate more the vibration stops. It's weird. Not totally sure but I think it usually occurs when I'm on a slight upward grade and right before the transmission need to shift to a another gear. Thanks.

 

Could be the bands or a valve body problem in the transmission.

 

Are we talking new transmission?

 

Yes we are.

 

Have you checked the trans fluid? Driveline? Anything? Most mechanics are idiots.

 

If you are vibrating under load but not during coast, I would start checking pinion preload maybe the yoke retention nut has backed off. Pinion bearings could be worn. If it were transmission, I believe the vibes would still be present on coast, as long as you were above 1500 RPM. Still must rule out driveshaft ujoints and centering bearing. Sounds more like a bearing issue right now.... output shaft bearing in transfercase?

 

Man this sounds pretty complicated for me, and the shops near me aren't much better. It's not undriveable and I can avoid the vibrations by altering the way I get on the gas. Just worried that this causing more damage the longer it goes.

 

Anything that moves or turns can vibrate. It can be hard to track down the exact component that is causing it.

 

Probably should add that it was at the shop a few weeks ago where they removed the transmission to replace the front main seal, and other leaks. Small vibration before then and they didn't say anything about the transmission being bad.

 

They had no reason to suspect it was. They were not there to diagnose it. They just R & R'd it.

As I said before, you just can't always look at something and see that it is bad.