Bad pinion bearing?

[BrianSanDiego]

Hey all,
My FJ has started to develop a noise.
It sounds like its coming from the rear end area.

Lets see...
Its kind of a metalic shhhh sound. Not a whine, or growl, or anything rhythmic about it. Its louder after driving on the freeway for a while. And maybe a big clue, is that it is noticeably louder for a little while AFTER accelerating hard. The pitch of the noise doesn't really change with speed, but maybe the volume does a little. When I shut down the engine and coase the noise still sounds the same. Its not related to accel or deceleration.

I am wondering if it could be a wheel bearing too. But when I drive S-turns the sound doesn't change. Its always the same kind of matalic hiss or shhhhh that get louder after I punch it.

The front of the diff, at the driveshaft, is pretty warm to the touch. Not hot, but noticably warm.

I've torqued the pinion nut. It was loose. Diff oil is clean and full.
Driveshafts are new so there shouldn't be any U-joint issues going on.

Does this sound familiar to anyone?
If so, any links to how to swap that suckka out?
Or any other tips?

I've never been into a Diff so any advice will be greatly appreciated!


Thanks once again, Brian.

 

[Pin_Head]

The front of the diff, at the driveshaft, is pretty warm to the touch.

I've torqued the pinion nut. It was loose.

Does this sound familiar to anyone?

You can't just torque a loose pinion nut without checking the preload. Chances are that the preload is way too tight, which is consistent with the heat. The noise is an indication of bearing failure. Just put a good used differential in there.

 

[BrianSanDiego]

Thank you Mr. Pin for the response.

I previously checked the FAQ and did a search on pinion bearings but missed the info on the preload being dictated by shims AND the nut's torque. I don't get why I wouldn't want the spec'd pinion torque now, but I can live with that.

I just tightened the pinion nut yesterday and went for a short drive. Should I just back the nut off to where it was before? Its obvious with the stake nut.

Also, I noticed the pinion bearing area was warm before I tightened up the nut. Does the warm diff, and the noise I described point at the diff as the cause of this noise? Or might there be another possible cause of a noise like that?

I am just trying to get a good idea of the problem before I plonk down a good chunk-O-change on a rear-end.

Thank you once again for your advice!!!
Brian.

 

[45Kevin]

I noticed the rear drive shaft had about 45deg of play and made a clunking noice when I let out the clutch, it turned out to be the pinion bearing. Put everything in neutral and see how much play is there.

On other vehicles, the hum was always from bad wheel bearings.

Both jobs are relatively easy but you do need to follow directions regarding torque specs.

 

[Pin_Head]

When the nut backs off, the shim pack "spins" and the wear decreases thickness, so the preload is often too tight when you torque it back down again. Tighten it to where is was perviously staked at. Chances are the pinion bearings (at least the outer one) is toast. Finding a good used differential is your least expensive option.

 

[BrianSanDiego]

Thanks guys. Wish I had discussed it first before messing with the pinion preload, but it seemed like the right thing to do at the time. Now I know.
Thanks for the help, much appreciated!
B.