Differential Bearing

[deeclue]

I'm in the process of replacing some leaking seals on my 89ix rear differential. I finally got it off the car and on the bench, and have it mostly dissembled when I noticed the bearing for the driveshaft/output shaft might be bad. But this is the first time I've done any differential work, other than changing the fluid, so really I have no idea.

I took a video of it on the bench - does this look/sound like the bearings are shot? In the video there is nothing left in the case so I feel like it should spin a little more freely. If they are I think I'll need to have a shop replace that one for me.

https://www.youtube.com/watch?v=6yVyZy6JffY

Thanks!

[AndrewBird]

Push down on the bearing and turn it slowly. Feel for any roughness. If you can feel anything, it is bad. Bearings can only be checked properly under load.

[deeclue]

OK I did that, and I didn't feel any specific spots that were rougher than others, but it was a pretty uniform not-smooth/rumble feeling. I did the same test on the differential's axle output shaft bearings and they felt perfectly smooth. I'm guessing that because this bearing is a bigger pain to replace that no one ever has. Looks like its time to call some shops and see who will replace it for me!

[AndrewBird]

It's not hard, but requires resetting the pre-load and pinion engagement/backlash.

[deeclue]

Yeah I found some other threads about it, looks more annoying than hard. I'll probably see how much it would cost to have someone do it for me. As long as this thing is out of the car I might as well get it all fixed up. Thanks for the info!

[The Dark Side of Will]

The scraping could be the pinion seal dust cover. Pry it up a little bit and see if the noise goes away.
Get a mechanic's stethoscope. It can give you positive diagnosis of bad bearings.
Or stick the point of a big screwdriver on the case near the bearing and put your ear on the end of the handle.

[deeclue]

update: I cleaned everything out as well as I could and pried the dust cover away a little and the sound did go away, still not sure how freely the bearing should spin though. But I had a long list of things I was working on so I replaced all the other seals/gaskets and got this thing back into my car. So far it seems like its driving fine so I'm guessing the bearing is fine to mostly fine. Thanks for the help!

[The Dark Side of Will]

Typical pinion bearing preload, even on old bearings might be 10 inlbs of torque. Add seal drag & carrier bearing preload and it won't be so easy to turn by hand.

However, it should *ALWAYS* feel smooth. If it feels rough, that's bad. You can also put the tip of a screwdriver on the case and the handle in your ear to listen to the bearings. They should have a smooth whoosh sound, not a rough, grinding sound.