E350 4M Rear Differential Failure?
 

All,

Good afternoon! I have a 2010 MB E350 4M that just hit 70k. There is a noise that has been present in the rear for a little while - it's a howling/rubbing and goes up with wheel speed. Not tied to RPM of the motor at all.. I'm a beginner aspiring self fixer upper and my first thought was it sounds like a wheel bearing is going bad on the passenger side. With the recent cold snap it got LOUD for a day, so I brought it to the shop. They are telling me the rear diff has failed and cannot be tested or rebuilt only swapped. Clearly something is wrong given the noise, but I asked if they checked fluid, could see what failed within, etc, they said it was "sealed" and couldn't visualize anything. The only option was to swap it for a new one for roughly $3,700. The noise has subsided and I have parked the car for the time being.

...One of the reasons I'm questioning the diagnosis... They also said I had a shock going bad on the front passenger side, which with our crap roads in Ohio is understandable, but it would be an additional $1,800! And this is not airmatic obviously.. I asked for a parts list and they have the OEM part at 267, then marked it up to 440/side then almost $1k in labor....for what would be roughly an hour of work...(I have new Bilstein shocks coming for under $400 to do it myself)

Is there anything I can do to confirm their diagnosis on the dif? I see there are drain and fill plugs on the diff that weren't even touched..so much for sealed. Should I check/change fluid? Any tests I can do to check that wheel bearing myself as well?

Thanks in advance!
SinisterCookie

That rear differential should easily go the 70k miles you've got on it, plus a lot more. I believe gear lube change is recommended at 100k miles.
I've got the same car, it's a 2011 but I know the parts are the same. I replaced the diff gear lube in mine at around 54k mostly out of curiosity. It was obvious when I drained it that the fluid was in great shape, barely even discolored, so it really didn't need changing. But that's ok, it was a minor expense for gear lube. At the time mine was still under ELW so I used MB spec fluid which is just a universal hypoid gear oil, 75w85. A lot of folks use M1, redline, etc., any good synthetic.
Anyway, that differential is absolutely not sealed - for that alone I'd get another mechanic, as you can check in about 2 seconds. It has a rear cover, as well as both a drain and fill plug.
If you want to verify fluid condition, you can do a drain and fill with fresh fluid and look at the drained fluid under a light - it should not have a glittery look to it.

There are a number of bearings back there that can be checked, both at the diff and at the rear wheels. Differential has pinion bearing and the side bearings, rear wheels have of course the bearings at the axle end flanges. You could try to get it raised up and try turning wheels, etc. but it may need to be (safely) run faster than you can spin a wheel. Any good driveline shop can check them all, plus if the rear axle needed servicing, same shop can repair, there's nothing special about that differential. I think W211's may have had some issues with inferior pinion bearings, but I've not seen a lot of issues posted about W212's. Of course, anything is possible. Don't forget about the driveshaft, it could be something as simple as something caught underneath and rubbing on it, or perhaps an issue with the DS center support bearing. Best is to get it on a secure lift and have it checked, by a competent shop this time.

Transmission fluid/filter service on our (if I remember right) pre-2012 cars is recommended at 40k mile intervals.

Thank you all for taking the time to review and reply! I will try an independent shop instead of the dealer and see what they turn up and report back.

@Mud I love the finish on the wheels! Very sharp! :D

My 2015's differential was replaced under warranty at 42,000 miles after describing the same.

Great advice above from Mud to get it checked at a specialty shop. I had a similar problem with my previous W220 chasing a low howling or rumble at speeds between 60-75 mph. It really wasn't that loud but due to the quietness in the cabin it was easy to focus on and fuss over. I wound up changing out the differential with a used one off of a low mileage wreck and still no joy. I changed out the driveshaft center support bearing with no change. I guess what I am trying to say is changing parts without a positive diagnoses may be frustrating and expensive! I recently changed my differential oil on my W212 at 96k miles and the oil looked barely used, same color as the new stuff I put back in.

Anyway, good luck on your quest! I am attaching WIS instructions for the front strut change out. Be very careful of the spring removal that you have it well controlled! I also recommend that if you don't already have a copy of the WIS/EPC program that you get one off of eBay. It's an invaluable tool for owning an MB and especially for the DIYer. I couldn't afford to own my MB's without it.

( I would be very surprised if your problem turns out to be the diff.)

Bob

X2 on the WIS/EPC available at very low cost. I keep a laptop out in the garage just with car info on it, handy to use, look up things especially when in the middle of something.
https://mbworld.org/forums/e-class-w...nual-cd-s.html

The work instructions are a great step by step procedure (I check youtube as well), and the EPC provides part diagrams/numbers specific to my VIN. Example is front struts - I checked the EPC part number A-212-323-59-00 and then found that Bilstein B4 22197665 struts are a suitable replacement. Plus of course you get info on strut mount/bearing, boots, bolts, etc. as needed.

The diff fluid interval on my 2014 is initially at 2K miles and then every 40K. Not sure on the 2010 model year interval.

Thats only on AMGs with LSD. All others are lifetime or 100k

Per the maintenance book at 2,000 miles -- "Replace rear axle differential fluid (only C 63 AMG, CLS 63 AMG, E 63 AMG, SL 63 AMG with AMG Performance Package and SL 65 AMG)"

She's moved on to greener pastures! A new E300 it is!