Whirring differential, clunking shifts. Four questions.

[Bishop]

I've got a slowly intensifying whirring sound from the rear end that I'm guessing is from the differential (matches the wheel speed, not the revs - could be a wheel hub I suppose), as well as a long-time clunking sound, usually when shifting from 1 to 2. My differential seals are leaking, and I'm worried that they've lost enough oil to cause damage.

Called the shop about the seals and inquired about the clunking sound and whether that could be bad differential bushings, and was told that my car doesn't have any bushings in the rear (this seems inaccurate).

My concerns are:
1. Even with new seals, should I expect worsening damage and eventual replacement - say within two years?
2. Is the seal replacement also a good time to have the shop replace the bushings/mounts, or can I just let those go?
3. If the differential is doomed, what's the best route for replacement?
4. Do I need a new shop? Any recommendations in Minneapolis?

Thanks in advance. Keep up the good work!

[danewilson77]

If you know your seals are bad, have you checked and maintained level properly? Not flaming, I guess I don't understand. You think the diff is empty and damaged now?

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[JupiterBMW]

Agree, if the seals are leaking, that should require extra attention to fluid level. Granted, its a pain in the ass to check diff level, but there's only about 1 liter in there, so it doesn't take much to leak before its empty...

The easiest way to keep an eye on it is to really move up the maintenance. Change the fluid every 10K miles, or even every oil change, that way you know it is always fresh and full. Also, take a good look at the fluid coming out. Color, smell, metallic sheen or glitter in it? Worse yet, maybe flakes? If you see flakes, I'd start shopping for a replacement.

Good news, you can get replacements online very cheap. Heck, in another month or so, I'll have my OEM diff for sale. But, keep in mind, you should get the one that is appropriate for your car. You can change the ratio, but you still want to get one correct. The cars all have different diffs depending on engine size and transmission type.

Good luck.

For what its worth, I just picked up a differential, used but in good condition, $100.

[Sockethead]

Clunking is probably rear diff mount. Thats the one that usually fails. It's the one that connects to the diff cover. You can visually check it for failure by getting under it with a pry bar and a flashlight.

BTW there are a shitload of bushings in the rear of our cars... Time to find a new shop..

[az3579]

The whirring and clunking is most definitely diff mounts. I replaced mine and the new ones are poly, so they whirr where it didn't before. No more clunking though!

[Bishop]

You think the diff is empty and damaged now?

I should have mentioned that I'm coming up on 160K on what I believe is the original differential. It's not dry, just old, leaky and making noise. Is now a good time to replace it, and if so what are my gearing options as far as used differentials from E46 variants?

Similarly, if I'm having seals replaced or a new differential swapped in, is that a good time to have the mounts done? What kind of damage should I check for from the clunking?

And any shop recommendations would be appreciated as well.

[Sockethead]

Axel seals are pretty easy to do....
There are a bunch of recent threads discussing gearing and LSD options
The diff has to be removed to do the bushings so yea that would be great time to do that

[az3579]

Doing the bushings during a differential removal should be mandatory. There is no reason to not do them at that point.

Cracked bushings are a giveaway that the bushings are shot. It'll be obvious if they're deteriorated.

[Sockethead]

Doing the bushings during a differential removal should be mandatory. There is no reason to not do them at that point.

Cracked bushings are a giveaway that the bushings are shot. It'll be obvious if they're deteriorated.
When I swapped out Charlie's diff. I had to flex the bushing to see the cracks in it so if you look at it and you think it looks fine, make sure you flex it with a pry bar