Rear end noise

DVCNick · 08-15-2019, 02:18 PM

When I first got my 06 MR, I was told by the dealer (and read online as well) that there is a certain amount of noise expected from the rear end (diff I guess?) when making low speed tight turns in a parking lot, etc. Mine has always had a little of this.

Well I hadn't driven the car in a while, and yesterday I cranked it up to take it for a spin.

It seems this noise has got significantly louder. Frankly doesn't sound good. Still only occurs in the same situation; low speed tight turns in parking lots. It wasn't limited to when the car was stone cold either.

Is there anything I can or should do to address this? New rear diff fluid?
Thanks.

Finnegan · 08-15-2019, 03:26 PM

Quote:

Originally Posted by DVCNick

When I first got my 06 MR, I was told by the dealer (and read online as well) that there is a certain amount of noise expected from the rear end (diff I guess?) when making low speed tight turns in a parking lot, etc. Mine has always had a little of this.

Well I hadn't driven the car in a while, and yesterday I cranked it up to take it for a spin.

It seems this noise has got significantly louder. Frankly doesn't sound good. Still only occurs in the same situation; low speed tight turns in parking lots. It wasn't limited to when the car was stone cold either.

Is there anything I can or should do to address this? New rear diff fluid?
Thanks.

There's a small chance it might also be a wheel bearing going bad. You could check that first. If that isn't the issue, you could always try changing the diff fluid (make sure you use one with friction modifier, that's the one with the +FM if Castrol) and see if that clears things up.

DVCNick · 02-17-2020, 08:26 PM

Just to update this thread... the car has been sitting for a while but I just took it to my guy who changed a bunch of fluids; oil, diff, brake, trans.. (also checked the alignment... might start a different thread about that. He also agrees that the sound is definitely the diff)

He put in Redline 75w140. According to the website, this has friction modifiers.

When cold it is still very noisy in tight turns, but warmed up, it is reduced; I'd say to about the level that it was when I bought it. Still very noticeable, not like you aren't going to not hear it, but definitely improved at least from when it is cool/cold.

I've found some much older threads from when the cars were new that seemed to indicate that some diffs were entirely replaced under warranty (M3s too). My guy basically said that the only other thing to do is "open it up" which I assume means rebuild it in some fashion.

I'm just wondering what modern common wisdom is on this now that the cars are older.

1) Doesn't "sound" good but ultimately "normal"/no harm or impact to proper function?
2) Just a matter of time until rebuild is required?

If the later, what is the process in terms of performance degradation, how do you know when it is really time, etc?
thanks for any input.

Manxman1950 · 02-18-2020, 02:10 AM

Quote:

Originally Posted by Finnegan

There's a small chance it might also be a wheel bearing going bad. You could check that first. If that isn't the issue, you could always try changing the diff fluid (make sure you use one with friction modifier, that's the one with the +FM if Castrol) and see if that clears things up.

This. I was becoming convinced that I had a diff problem, but it turned out to be the LF wheel bearing😐

DVCNick · 03-12-2020, 09:08 AM

Just one further update, I've driven it probably a couple hundred more miles and now it is very noticeably better. Once warmed up, it is very faint/definitely much less noticeable than when I bought it.
So I'd recommend the fluid above (or probably the other mentioned with the friction modifiers) and then a little bit of driving as a first cheap solution to anyone experiencing this issue.

08-15-2019, 02:18 PM	#1
DVCNick New Member 8 Rep 27 Posts Drives: 2006 M Roadster Join Date: Dec 2017 Location: Greenville, SC iTrader: (0)	Rear end noise When I first got my 06 MR, I was told by the dealer (and read online as well) that there is a certain amount of noise expected from the rear end (diff I guess?) when making low speed tight turns in a parking lot, etc. Mine has always had a little of this. Well I hadn't driven the car in a while, and yesterday I cranked it up to take it for a spin. It seems this noise has got significantly louder. Frankly doesn't sound good. Still only occurs in the same situation; low speed tight turns in parking lots. It wasn't limited to when the car was stone cold either. Is there anything I can or should do to address this? New rear diff fluid? Thanks.
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02-17-2020, 08:26 PM	#3
DVCNick New Member 8 Rep 27 Posts Drives: 2006 M Roadster Join Date: Dec 2017 Location: Greenville, SC iTrader: (0)	Just to update this thread... the car has been sitting for a while but I just took it to my guy who changed a bunch of fluids; oil, diff, brake, trans.. (also checked the alignment... might start a different thread about that. He also agrees that the sound is definitely the diff) He put in Redline 75w140. According to the website, this has friction modifiers. When cold it is still very noisy in tight turns, but warmed up, it is reduced; I'd say to about the level that it was when I bought it. Still very noticeable, not like you aren't going to not hear it, but definitely improved at least from when it is cool/cold. I've found some much older threads from when the cars were new that seemed to indicate that some diffs were entirely replaced under warranty (M3s too). My guy basically said that the only other thing to do is "open it up" which I assume means rebuild it in some fashion. I'm just wondering what modern common wisdom is on this now that the cars are older. 1) Doesn't "sound" good but ultimately "normal"/no harm or impact to proper function? 2) Just a matter of time until rebuild is required? If the later, what is the process in terms of performance degradation, how do you know when it is really time, etc? thanks for any input.
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03-12-2020, 09:08 AM	#5
DVCNick New Member 8 Rep 27 Posts Drives: 2006 M Roadster Join Date: Dec 2017 Location: Greenville, SC iTrader: (0)	Just one further update, I've driven it probably a couple hundred more miles and now it is very noticeably better. Once warmed up, it is very faint/definitely much less noticeable than when I bought it. So I'd recommend the fluid above (or probably the other mentioned with the friction modifiers) and then a little bit of driving as a first cheap solution to anyone experiencing this issue.
	Appreciate 0 Quote