[redgt00]

Hey all - Looking for some help in diagnosing some rear road noise.
2011 E90. 328i RWD. 110k miles

Here's a sound recording - Phone is in backseat. Speed is about 30-35mph
https://youtube.com/shorts/-O5lCgHUfRg

My daughter drives this car and it had a bad TPM sensor for awhile. I noticed one day her tire pressure in a couple tires was way low. The tires had actually worn unevenly. My tire shop advised I put on new tires and TPM sensors. I did this, but noise is still there. They put a note on my invoice that a rear wheel bearing is starting to make noise, but didn't say which one. They didn't even mention this to me. Is it possible the uneven tires damaged something?

I initially thought it was a wheel bearing based on the tire shops note and got all the tools and parts to swap one. When I started diagnosing which side it was on, I kept hearing something on the opposite side until I eventually heard noise coming from the differential.
-No play in wheels during shake down test
- No change in sound under lateral load (cornering both directions)
- Diff makes clicking noise when someone spins a wheel. Listened to this with stethoscope.
- diff is quiet when wheels spin and car is in gear on jackstands. Couldn't get my wife to rev it up very high though while I was under it.
- loud humming noise when driving
- No clunking

Any thoughts?
Could the diff be bad? I'm not sure what could cause that. Would it be best to swap with a used one form ebay? Any good rebuild kits?

I'm also considering a diff fluid change, but I'd be really surprised if that fixed the noise. I have everything to do a wheel bearing, but I can't pinpoint the side that's bad. I can only her noise from the differential. I'd just be really surprised if the differential is damaged at such low mileage.

[redgt00]

Anyone?

[Brian86]

Sounds like a bad ring/pinion, but it's always hard to diagnosis over the internet so take it with a grain of salt.

They usually don't go bad unless they were run out of oil. Is there oil in it?

I assume mine was run out of oil, judging by the leaking input seal, but didn't go bad until perhaps 50k or 100k miles later. Interestingly mine was very intermittent. It would be totally quiet, except when slowing down to street speeds after a long highway run in cold weather... but boy did it sound bad when it was singing.

Mine also had some non trivial spalling on the side gears when I opened it up.

www.car-part.com

punch in your vin number. The car part web portal is very good about cross-referencing parts. Should find one for about $200.

[Brian86]

Oh, forgot to mention.

The clicking is normal. The side/spider gears are loaded together pretty tightly. Both my old bad one, and my used good one had a light click.

With the carrier out of the car you can feel it when turning the output shafts.

[redgt00]

Originally Posted by Brian86

Oh, forgot to mention.

The clicking is normal. The side/spider gears are loaded together pretty tightly. Both my old bad one, and my used good one had a light click.

With the carrier out of the car you can feel it when turning the output shafts.

Appreciate your input!
Sounds like I need to check the oil in it. Thinking I'll drain it then top it back off and see how much I can get out.
Probably will end up taking it somewhere if that doesn't change anything.

[335i54n]

more than likely a wheel bearing, its a lot more common. you really dont need a lot of speed up on stands to locate the noise (long screwdriver to ear) and an open diff you can hold 1 wheel if it help find the noise

[redgt00]

Originally Posted by 335i54n

more than likely a wheel bearing, its a lot more common. you really dont need a lot of speed up on stands to locate the noise (long screwdriver to ear) and an open diff you can hold 1 wheel if it help find the noise

That's what I had originally thought but I'm struggling to figure out what side its coming from. There's zero play in the wheels and no change in sound under a lateral load. I have a bearing ready to go. Just don't know what side to swap.

I'm going to do a fluid change tonight. While the car is up I'll listen again.

[redgt00]

Changed diff fluid. Seemed to be plenty of oil in there. That didn't make a difference.
I had someone drive the car with me sitting in the back. Noise sounded louder on the drivers side. I swapped that wheel bearing, but made no change.
Thinking I'll take it somewhere and have them look at it. I'm getting tired of trying to diagnopse this thing. Hopefully nothing wrong with the differential!

[redgt00]

Felt I should add the resolution:
Twas the other wheel bearing (passenger side).
It had just started going bad so was audible, but there was no play in the wheel.