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Discussion Starter #1 (Edited)
I've been researching this issue like crazy for the past two weeks and I can't put my finger on it. I've got this weird groaning/howling noise that comes up on the M5 around 40mph and up and it seems to sound the loudest around 55mph. I replaced the differential and transmission fluid yesterday but no dice - the howling is still there.

It seems to be related more to speed than with the engine. It stays constant with whatever speed I'm in regardless of throttle or even if I'm coasting in neutral. Also, when I'm slowing down to a stop, I can hear this kind of groaning noise that sounds like an electric motor that's winding down, which I'm 99% sure comes from whatever source the howling comes from.

Power steering fluid level seems to be ok and it doesn't change when I'm turning. Edit for more context: car is a 2002 and just hit 114k miles on the dash

Any ideas? Or maybe a recommendation to an Indy mechanic in northern Virginia/DC who can diagnose it (that doesn't cost $175 :frown)
 

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Discussion Starter #3
No video yet but I'll try to get that on my way home from work.

By #1 are you referring to that gasket? Now that you mention it, one of my rubber jacking points broke off but does that really cause a groaning noise? I would imagine it wouldn't make a winding down noise but i can probably just go to the dealer and pick that up today.
 

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No video yet but I'll try to get that on my way home from work.

By #1 are you referring to that gasket? Now that you mention it, one of my rubber jacking points broke off but does that really cause a groaning noise? I would imagine it wouldn't make a winding down noise but i can probably just go to the dealer and pick that up today.

I'm sorry, the url from that diagram kind of 'stuck'. I meant this diagram here: with the OSV * 2 of them).

And I have heard of the missing jacking points causing a whistling or howling noise. Perhaps we shouldn't assume that the 'winding down' sound is related to the howling. Maybe it's just coincidence and the the winding down is belt-system / fan clutch related, somehow (?).
 

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Discussion Starter #5
Gotcha you're right, I'll try the jacking point first. As for the oil separators, how would I check that? Just see if there are any leaks or something?

The winding down makes me think it could be related to the belts or the alternator as well
 

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Discussion Starter #6
Update: didn't get a chance to record a vid because I was on a phone call on the way home but I got jack pads from the dealer - no dice. I'm thinking it could be related to the a/c system? I hear a little bit of a whine when the a/c is on as well. I'll probably take it to German Auto Group of Alexandria, unless someone can suggest a better shop?
 

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have you tried thicker oil to see if the noise subsides? Or if you want to go through the effort procure some fine sawdust and fill into the diff to see if that quiets down the noise. (If it doesn't you'll have one heck of a time cleaning up the mess you've made). What you described sounds more like a wheel bearing going bad, but then again without any other input we're just guessing. Do you know/trust this mechanic? If yes please keep us posted as to the outcome.
 

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Discussion Starter #10
I have rebuilt a diff before but at this time, I don't have a proper garage or workspace to do it. Yeah, I trust these mechanics - they didn't even charge me for the diagnosis. They found out it was bad easily by just putting the car on a lift and running it. At this point, I'm just waiting on Clemster to see if I can squeeze onto his schedule to get one of his diffs he has.
 

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Check you remote oil filter and mounts. If the filter housing is touching the fender it will transmit oil pump noise. The mounts go bad.
 
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