Noise in rear of car plus diff fluid everywhere?!

[Mike1261]

I've been hearing a noise in the back of the E53 the past week or so and seems to be getting worse.

It happens at low speeds around town, bumps seem to set it off. Highway no noise, smooth roads no noise.

It sounds like a low chirp as the best I can describe it. I thought it might be the lower control arm moving around in the slot because the nub on the frame that secures the eccentric washer in place is damaged and not able to hold a toe alignment. Figured on bumps it was moving around. But it doesn't seem to be.

I crawled under the back this evening and was shocked to see fluid sprayed all over the passenger side under the car and over the tow hitch.

Attached is a pic of the area where the axles go into the differential and there is a gap that isn't present on the driver side of the diff. I'm guessing that's where fluid is coming from as all the wetness seems to originate in that area.

Does that make sense? I don't know the mechanics of the rear axles/diff and how it's all pieced together. What do I need to do to fix it?

I recently replaced the passenger side lower control arm bushings. The old ones were totally F'd. I had to cut them out with a sawzall because the bolts were seized inside the bushings. I'm wondering if correcting the rear control arm geometry put stress onto the axles in a way that's causing this issue? Seems awful coincidental to be on the same side immediately after the bushing replacement.

Thoughts?? Thank you!

[Purplefade]

Solely based on your description and prior work, it wouldn't be unreasonable to consider that hammering on that control arm or otherwise adversely banging on or letting weight hang on that axle shaft may have compressed the axle seal... IF that happened it would be possible for gear oil to leak from the differential causing the low noise that you're hearing. There is some small gap between the axle and the housing, I can't tell if yours is excessive or not, but your description makes me think gear oil, which makes me think that sides seal has been compromised.


To fix it :-( pull the axle, replace the seal, put the axle back and refill with gear oil (I used LiguiMoly Full synthetic when I did mine) - and if you haven't already, grease and replace the cv boots while you have it out.

[Purplefade]

A decent test would be to pull the fill bolt on the rear diff and make sure it is full, if not, fill it and see if your noise changes and watch the leak. If it changes, goes away, leak gets worse, etc, etc, you'll have more info to go on - and it's cheaper than just jumping in :-)

[Mike1261]

I'm picking up a seal at BMW tomorrow and will work on getting that changed out hopefully on Sunday.

I'm kinda wondering if maybe something in the control arm replacement caused the C Clip holding the axle into the diff to pull out a bit. I don't know if that's likely or possible, but either way the whole thing is coming out and getting replaced with the new seal either way.

I'm ready for this car to stop breaking now... I listed all the repairs I've made over the past 18 months and I'm at over 40 now. Most cheap or even free, but all annoying lol. I have a new passenger side window regulator sitting in the garage too so I can fix my wife's window next. My driver side regulator broke 3 months back so at least I know it's an easy job!

[Purplefade]

Heard that!! I “bundle” the little things and do them in batches so that I get a bunch done at once and don’t, usually, have to mess with it again for a bit. That said, once you get the bigger things ironed out - you be ecstatic to get to drive it for a while

Keep us posted on your success with that seal and good luck!


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