Loose Pinion Nut

Yesterday Jenny showed up at church saying her Jeep was making a funny noise. It sounded like it was from the drive shaft.

I drove it back to my shop and noticed that it only made noise on deceleration. Even the slightest load from the engine made it quieten down.

I guessed it had something to do with the pinion as that is the only thing that would move around depending on load. Her Jeep Cherokee has the Chrysler 8.25 rear end.

At the shop, her Jeep would hardly back up but went forward just fine. I used 4wd to back up to pull into the shop.

Once on the lift, I inspected the drive shaft first by feeling of the U joints to see if either was hot. Then I felt the differential and noticed it warmer than normal. I suspected a pinion bearing.

I pushed on the rear of the drive shaft ans saw the pinion move. There was a lot of movement so knowing this is a tapered bearing, I suspected it must be loose.

I quickly dropped the drives haft and soon saw the trouble. The pinion nut had backed off. I guess if it had not been for interference with the u joint it would have come completely off.

I remembered that a couple of years ago when I replaced the pinion yoke that I did not use lock tight on the threads. This time I did.

The punch marks I made before were still visible, so I put the nut back to align the marks and the preload felt about right by hand. So I left it there for the lock tight to dry.

A test drive indicated that the noise was completely gone. I guess we caught it in time before th ring gear was damaged.

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