[Guest]

Hi all, newbie here ...

My 91 Jeep Cherokee (2WD, A/T, 200K+ miles) has a pronounced vibration and loud noise between 50-60 mph. The noise appears to be coming from directly under the body.

When I recently replaced the U-Joints I noticed the transmission output shaft could be wiggled about 1/16" in both the vertical and horizontal direction.

Could a bad rear A/T bearing cause the noise and vibration? If so, are they difficult to replace? If not, could you please give me any suggestions as to what the problem may be?


THANKS IN ADVANCE!!

 

[Chris_MJ]

Yes, that could definitely be a problem. Output shafts should be firm and only move in one direction -- rotationally. BUT! As obvious as that may be, consider checking to make sure all your wheel lugs are tightened down and that all your tires are still in balance. Either of those things will cause vibration. I missed a bolt once and had four tight and one finger tight. Vibrated at 52-55 mph.

Also, before you go changing it out, make sure your new u-joints are still good and that the rear cross has seated correctly into the rear axle yoke. I lost a driveshaft once when I intalled it at night. It vibrated at about 50 mph and then went flying down the road when I hit 65.

But as for the bearing, it could be easy or it might just plain suck. The easy chance would be that you could remove the bearing without removing the shaft and even by chance not have to remove the tranny. In most cases and a reality situation is that you could have to remove the tranny, open it to remove the shaft and use a bearing puller to get it out.

There is a possiblity that you could be really lucky in that you have 2wd in that the easy way might be possible. The tailstock that is added for 2wd models might be able to be removed while in the vehicle. This would greatly increase the chances of being able to do it with tranny still in the truck. But I don't know the AW-4 2wds at all so I can't tell you if that's possible. I've got a 2wd manual and know a little more about that.

If you plan to try replacing it, don't forget to buy an output shaft seal with the bearing.

 

[130]

Are you sure that you reinstalled the driveshaft in "phase"

 

[Guest]

I know if the rear transmission mount to the cross member is failing --on a 4 x 4 --it allows the transmission to drop down, placing stress on the exhaust system --this in turn shows up as a vibration and noise inside of the cab --

 

[Chris_MJ]

Sycho,
If he had the u-joints replaced on the original driveshaft, is there a way he could be out of phase?

 

[Guest]

Thanks all ...

I appreciate the help. The tires are rotated & balanced regularly (every 6000 miles or so)and it's been less than 1000 miles since last done.

The vibration and noise was occuring to some degree since before I replaced the u-joints ~7000 miles ago. The noise wasn't entirely eliminated, but recently got much, much worse.

The drive shaft is "in phase" - I marked it and the pinion yoke before removal. However, I didn't have the shaft rebalanced after replacing the UJ's so if it's out of balance it may have caused the bearing to wear.

I'll know more tomorrow when I take a closer look. Thanks again!

 

[Guest]

Re: Thanks all ...

If you can move you slip yoke upNdown and leftNright check the slip yoke spline they maybe wornout or the look at the output shaft spline.

 

[Andytron]

Re: Thanks all ...

Chris, the answer is yes. It's possible to flip one or both yokes 180 deg out.