I am new to the forum having just signed up after finding some really great info here regarding a problem I am having with my 2001 SLK320 (as you know, should be almost identical to the Crossfire’s).

The issue I have is the somewhat common differential hum/whine at certain high speeds as described and diagnosed in these older threads:
https://www.crossfireforum.org/forum/crossfire-coupe/28363-80-mph-rear-end-noise-dealer.html
https://www.crossfireforum.org/forum/crossfire-coupe/15777-humming-noise-when-driving-over-50-mph-2.html
https://www.crossfireforum.org/forum/crossfire-coupe/12076-rear-end-noise-2.html

The above threads have some great details regarding the problem (much more than I’ve found anywhere else) so I am already grateful for that, but they are a few years old, so I am hoping to get some fresh input now that many of the vehicles are no longer covered by warranty and likely have some higher mileage on them

After reading those threads I am convinced that my car suffers from the same “factory defect” differential issue, my car currently has about 78,000miles on it, always maintained by MB and never abused (it is my daily commuter). It sounds like this is a very expensive repair, especially since I am not likely to get any help from MB or the dealer given the car’s age, so I am looking for any help or advice you guys may be able to offer:
· If I leave it alone, and live with the annoying noise, am I going to get stranded somewhere? My girl uses the car on a regular basis and I want to be comfortable knowing she isn’t going to have a problem. I also go on frequent road trips and don’t want to have an issue when I am hours from home and/or a dealer.
· Has anyone found any aftermarket solutions? Maybe a performance diff? or more cost effective option than a factory replacement?
· Has anyone had any luck buying a used unit and having a shop rebuild it? Then getting the dealer to install? (I’d worry about putting out a fair bit of $$ and having little leverage should something go wrong)
· Does anyone have any official bulletins or something I could show my dealer? Maybe if I can prove that this is a known factory defect they may help me out a bit

Any other thoughts/input is greatly appreciated.

Thanks!

 

I had or rather my wife had a whine from the diff in a Mustang and she solved it by turning up the radio. When the radio became too loud because the whine was too great she informed me of the problem, too late for the diff as the wear pattern had ruined it. Faced with a large bill for a new diff or less to replace the bearing which had failed initially I opted for the bearing and figured my wife could live with a slightly louder radio to drown out the lesser whine which was now present permanently.

Moral, fix the bearing if that's the problem, before it gets too bad.

 

From what I've read the ring gear itself is actually the problem?? And it sounds like in most cases the entire diff was replaced.

 

Any chance of putting it up on a lift and running it to speed? You would want to support the wheel ends of the axles to near "ride height", but it would give you a chance to hear it.

Of course, someone would have to be in the vehicle up on the lift.

A shop with safety concerns might not do it...

 

The dealer won't that at a high enough speed, they did it at my 55mph or so and didn't hear anything.

To be clear though, I am pretty sure I know what the issue is, since the symptoms are EXACTLY the same as the numerous owners in the threads I noted above, all of which turned out to be a known flaw with the differential. So as much as I appreaciate the input; I am looking for advice to remedy the issue with the differential, not diagnostics.

Thnx

 

Get a new diff or a performance replacement then, but you knew that.
Improper shimming can cause whine and after a while the wrong wear pattern will cause a permanent whine.
There are mentions here of half sheared pins, maybe that's your problem. Did you have it new, my guess is that you did not so maybe it's been abused a bit before. No manufacturer is going to look into replacing it even if you had it new.
Replacing it will stop all the whining.

 

Yeah, you're probably right. I've got a decent relationship with my dealer, so I am trying to put together a case with all the examples I can find of owners who have had to have their differentials replaced so I can argue that it is infact a factory flaw (many of the members here had theirs replaced while the car had under 30,000miles on it) in hopes that MB Canada might throw me a bone and help out by covering some of the costs. It won't take me very long to make a decent case, so I figure the worst that could happen is that they say "no".

I am the second owner, the original owner was an elderly asian guy, I doubt he drove it very hard. Car has full dealer service records right from new.

You mention performance diffs, any suggestions? I've read about this wavetrac thing, but it sounds like it only replaces some components? but given my circumstances I'd rather replace all the components.

Does anyone know a good place for me to source a remanufactured unit should I have to?