Well, the well loved and cared for GLK got the dreaded rear diff failure diagnosis today. Excessive whine from the rear end and when the mechanic opened up to check the oil there was plenty of oil but also plenty of metal flakes... Guess I'll call around and see what options for a rebuild and/or replacement.

 

There are good sellers on eBay, get one with a warranty.

 

I'd do what Mmr1 recommends. Or if you're lucky enough to have a well-stocked boneyard nearby, go pick one from a donor car. These diffs really don't fail often, so the chances are overwhelming you won't have any issues with a used diff unless it's been in a flood.

Oh, and the rear diff isn't the "dreaded one" - that would be the front! ;-)

 

Sorry to hear that OP, how many miles on this one, when was fluid last changed? Do you tow? Original owner?

 

What does that refer to? "dreaded" failure??
Never read about it.

Year model and mileage?? Where? - ie., where salt is dumped on the roads?. History of past repairs?

In my 50+ years of dealing with vehicles (wrenching autos and motorcycles), I've NEVER experienced a "rear diff" issue ... EVER.
Heck, my wife's E320 got 330,000+ miles with no significant probs. Jeep w/135k miles, no prob. 2014 GLK350, 95k miles, no prob.

"who" determined the differential is bad? Yea, it's expected to have a bit of "shavings" after some mileage. After all, there's ring gear, pinion gear, spider gears, side gears ... all meshing together.

I'd get a second and third opinion on the "issue*.

 

In my 50 years of driving I've had one failure. That was on my second car, a 1969 Thunderbird with a 429 cu. in. and posi.

 

As others said it’s rare to loose a rear differential, I would get it on a lift with someone inside operating the drivetrain spinning to be sure it’s not a bearing or nearby component like U joint . Use a stethoscope. You said you had oil which I would have expected no oil if it was bad , metal can be normal . Hopefully it was not diagnosed properly and is a bearing or ujoint . They sell for about 50$ remote microphone system you attach to parts near the noise to pinpoint it. I think it’s like 3-5 microphones on at once so you can change between microphones to pinpoint noise . Just a wine I would not get to worried about , is there any clunking when shifting , that could be a u joint , an infrared thermometer could pinpoint a bad bearing that’s getting hot. Take it somewhere else to be looked at. Are gears loose? Anything visable that looks bad inside of differential ? Run motor and wheels with cover off and someone looking inside it. Without looking at the layout I guess it could be one of the 5 sets of bearings and 5 U joints that are not inside the differential , my numbers are probably off though. All those are cheaper than a differential.

 

How many miles does your car have?

 

Sorry guys disappeared a bit after posting this and getting parts/repair lined up with a mechanic who was willing to put in a used unit. Both a local auto shop here in St Louis along with my family mechanic outside of the city diagnosed a failing pinion bearing on the rear diff. We were having quite loud rotational whine while driving the vehicle.

2010 model, my now wife bought it new, diff oil never changed, just crossed the 100k mark. I was optimistic the noise would have been a carrier bearing or at best perhaps a rear wheel bearing. However the latter didn't seem likely given there was no change in sound while turning or pitching any weight from side to side. Both shops used stethoscopes on the diff while vehicle was on the lift with wheels spinning. Also, there was a good amount of glitter that came out with the fluid when the first shop removed the plug.

Used unit is in. Noise is gone. Fingers crossed this one is good to go for awhile...

 

Glad you got it sorted out. It’s an unusual failure, but not unheard of.

 

Thanks for providing an update OP.

 

Rear diff fluid change is a 15 minute job, very easy, quick and cheap to DIY.

Front diff is pretty easy if you have a right tools as well.

197k km on the '13 GLK, change the diff fluid every 50k, runs like a dream.