Ok I know this is the wrong forum for this but hopefully you guys will help me out. A buddy of mine has a 1993 Jeep Cherokee XJ it has a 6 Inch Rough Country X-series lift and 33 inch tires, 4.0L inline 6 and upgraded gears front and rear (not sure what ratio) the rear axle also has a limited slip diff. Well we towed his boat with it on a fishing trip its a 16 foot boat and on the way back his jeep was making a rattling sound in the rear end when he let off the gas. Well after a few weeks it is worse it is a nasty sound that can come and go as it pleases. It sounds like driving on a blown out bearing that is missing a few *****. We have checked everything I could think of and yesterday when we had it off the ground and in neutral I spun the rear driveshaft and it spun by itself, the rear tires did not spin at ALL. So I put it in park and spun a rear tire and they rotated almost without any resistance but the front ones will not spin. I was told it could be excessive backlash in the ring and pinion but im not so sure any help would be appreciated.

 

Did you check the u joints? Take the shaft off and spin the little caps by hand. This will also have you set up for checking the lash in the pinion. While at it, pull the diff cover off amd check the berrings surfaces, and for debris in the oil that pours out.

My guess is the ujoints on the shaft. The lift puts more stress on em with the higher angles - makes them not last as long.

 

You spun the driveshaft and the rear wheels not turning at all says the diff has stripped gears, hardly just excessive backlash. {I'm holding back a guffaw here .. not to you but to the idiot who blamed it on 'backlash'}

If you spin one sides wheel in park, the other will try to turn the opposite direction, depending on the health of the clutches {open rear spins opposite, freely}.
However if the other side wheels spin the same direction, the ring or pinion or both is shot.

But the real question is why were you on the highway in 4wd?

 

could be a blown carrier bearing. ive seen them blow out where the truck will only go in reverse or drive due to the carrier shifting toward or away from the pinion . naturally if the rear end is going clunkity clunk you kinda want to open up the rear axle cover and see whats going on anyways

 

Checked the fluid in the diff and the magnet there were no metal shavings so i just filled it with new fluid. Now the pinion seal is leaking and fluid is getting on the drive shaft and then getting sprayed everywhere. I checked the U-joints they are fine. Will prolly just end up getting another axle from the junkyard. If it has stripped gears then how can it still move when in drive? And the 4wd was never used on the highway it was only used for offroading. This jeep can't even get up to 60mph because the tires are too big to be balanced and vibrate at high speeds, everything was fine until he towed the boat.

 

I really do not understand your reasoning.

You said you jacked it up and turned the rear driveshaft with trans in neutral and the wheels didnt move, right?

Then you said you tried to turn the front driveshaft while in park and it wouldnt turn, right?

Now think about it.

If the pinion seal is puking, seems to me that answers the question. I'd be very surprised if there's no evidence externally that the pinion carrier is trashed.

Does that jeep have manually selected 4 wd.. or does it kick in automatically somehow. I think you guys better figure out how it got in 4wd before you trash the next one. Did he use 4wd to pull the boat trailer off the ramp?

 

Problem fixed thanks for the help guys my friend says thanks too. We just ended up replacing the axle with one from the junkyard and upgraded the gears to match the front. We also upgraded the drum brakes to disc.