Uh Oh...Rear Differential Problems... - BMW Forum

441tech · 08-09-2008, 04:02 PM

Here's the dealio:

I've had a vibration in the rear end for sometime, and has recently gotten worse. I put it on jacks and hand-spun the rear wheels, and it sounded like a rythmatic, rotational flat-spotted bearing inside the diff. Car is a '99 323i with 165,000 on the ticker. Does anyone know of these having diff. problems later in their life? The vibration can be felt at all speeds, but is the worst between 30 and 40mph, and when accelerating it is amplified. It also gets amplified around corners. I know it's in the diff. because I disconnected the output shafts and rotated the driveshaft and it still made the same noise.

Here's what's been replaced since I've had the car:

- Front struts and rear shocks
- Trans./driveshaft rubber coupling
- Center carrier bearing assy.
- Rear wheel bearings
- All brakes and related components
- Wheels and tires

I did not check the fluid level, nor has it ever been replaced to my knowledge. However, the entire diff. and surrounding area are bone dry...No signs of any leaks. The only thing I haven't replaced are the output shafts...The inboard joints at the diff. felt a little worn and stiff, but as I mentioned before, the noise still comes from the diff. with the shafts disconnected. And yes...I'm going to replace the output shafts - To my knowledge, they are the originals as well. Expensive buggers, though.

I guess my question(s) is: What's the problem? Bearings in the diff. housing? Gears? Old Age? Is my differential repairable, or should I just call some 'yards and try to find a low-mileage diff? Does BMW have a reman program?

Any help/insight would be greatly appreciated.

Thanks in advance.

441tech

sprintman · 08-10-2008, 02:36 AM

Always replace diff and g'box oils regularly. OEM stuff isn't that good to start with and 'lifetime fill' is total bs.

441tech · 08-10-2008, 05:49 PM

So would it do any good to change the fluid now? My guess would be no, since I would imagine the damage is already done.

BTW...What's a good fluid for this diff?

441tech

AlpineSixAndSeven · 08-10-2008, 05:58 PM

^ sounds like it is already dead.... sounds like it is time to upgrade to a LS(Limited Slip) unit!

441tech · 08-10-2008, 06:06 PM

Shiza...I didn't know you could get a limited slip. In fact, I thought that was already in there since everytime I broke 'em loose both wheels started diggin'...Where's a good place to get replacement diffs?

441tech

sprintman · 08-10-2008, 07:47 PM

Redline 75W90 is good imo.

AlpineSixAndSeven · 08-11-2008, 01:03 AM

This is a nice Non lsd unit if you need a replace ment quick
eBay Motors: BMW 3.46 NP Rear Differential E46 325 325i SEDAN (item 220250450740 end time Aug-24-08 14:54:53 PDT)

I'll look for a LSD unit for you to if you decide to go that route...

441tech · 08-12-2008, 02:51 PM

Thanks Alpine!

Looks like a pretty nice unit...Are they reliable? Have you ever bought any of their reman stuff? I'm assuming this is a reman unit...And if you wouldn't mind, I would like to know where to get an LSD unit...

441tech

AlpineSixAndSeven · 08-12-2008, 09:24 PM

thanks friend bought a diff for his 318i and it worked till he crashed it

I'm still looking for a Lsd unit i havn't forgot about you

titaniumbullet · 08-16-2008, 01:41 PM

you need to replace it.... its gone..... I would do an upgrade LSD (limited slip diff) make sure you maintain the fluids and what not so your not running into this in the future.