Hey there, fellow W204 owners!
Mine is a 2013 C300 4Matic that I picked up around 3.5 years ago and is now at 122,000 miles. I have tried to keep in top shape. Upon purchase, I replaced the drive shaft joints, water pump, timing cover gasket, new shocks, struts and a handful of suspension components and had a major service performed. I have stayed on top of regular service intervals since. I also fixed it up with new OEM HID headlights, AA/Carplay module, and Brabus springs and wheels.

Last week, I went to work, drove to a meeting and returned to the office but in the afternoon, I had to go out again but when I turned the key, absolutely nothing. It turned out to be the dreaded Electronic Steering Lock (ESL). While at the shop, I asked that B Service be performed.

Rewind back a few months: the car started making a noise like a bad wheel bearing or a dragging brake pad. A couple of superficial inspections revealed nothing. Other than this noise, car has run like a champ.

Fast forward to today: The shop just called me. Good news - EIS fixed, service performed. (cost: $3K). Bad news: the noise I have been hearing is coming form the transmission and they found a ton of metal shavings in the transmission oil pan. They tell me the car may run a few days or a few years but impossible to know without a teardown. They suggest replacing it instead of going through the expense of the teardown.

New transmission is $10K.

This kind of hurts as I bought this car with the intent of giving it to my daughter who is getting her license this summer. Based on these developments, looks like I'm facing the grim reality of having to let it go. Absent paying about as much if not above the fair market value to fix it, is there a way to save it?

Insights appreciated.

Picture of oil pan sent by shop:

Metal shavings on magnets

 

Being a 4matic, chances are it's the transfer case giving up the ghost, not the transmission itself. If you're really handing this down, I'd save yourself the grief of trying to get it right. And if you don't need AWD, get RWD for less complexity, regardless of the brand you go with.

 

$10K for a new transmission, fix the issue and probably never have to deal with transmission related issues again. Hopefully comes with a good warranty, parts and labor.

Could always have the transfer case pulled and inspected, see if it is the cause of the metal shavings. Then you are looking at $1,000 for a remanufactured transfer case + labor.

Could always search around for a low mileage used transmission. Swap them out.

You could always search for transmission shops in your area and see if any have experience with Mercedes. See what they recommend.

Could always pull the drain plug of the transfer case and inspect the fluid that comes out of it. In the 4matic the transmission fluid travels thru the oil cooler then back into the transmission and also to the transfer case, that fluid in the transfer case flows back into the transmission. If you pull that drain plug and see metal coming out theres a good chance thats the issue.

Then again it could be something else.

 

The metal particles on the magnets don’t look all that bad (but not good, either) because they’re fine, powder like and not larger spall. The issue is that the noise indicates a probably dead bearing somewhere. If it’s the one in @TimC300 ‘s figure 1, that will quickly ruin both of the front axle output gears. The 722.9 is very repairable, but the problem is finding a shop that is familiar with it.

A teardrop down and rebuild shop, if you can locate one that has references on MB transmissions, would probably be in the $3k-$5k range and take maybe 10 working days. @habbyguy has posts on what’s involved in a transfer case rebuild, so a $1k estimate is maybe a bit low.

If you do replace the C300, make sure that what you get has Toyota (Lexus) or Honda (Acura) written on it. In our little fleet, most of which get very hard use, the Hyundais aren’t getting the job done. Half of the MBs were replaced by Ford pickups out of necessity. All but 3 of the rest are turning into Hondas which are, honestly, very impressive. We don’t have any Toyotas, but I have personally had them that survived floods, collisions, and multiple drivers.

 

Great information and sound advice - thank you. I noticed that with the transmission oil change, the noise has noticeably subsided. Nevertheless, it seems that this is going to be a significant and unavoidable issue. I guess have some deliberating to do over the coming days.

 

You have many good transmission shops in San Diego. One highly rated one, is Transmasters Auto Care, and Mercedes is on their list of cars they work on.

 

no surprise there because the transfer case and transmission share fluids if I recalled correctly.

 

Other than the dealership, I regularly take the car to South Bay Autohaus. They are reliable and great. My main concern here is whether repairing it is cost-effective. The car is 13 years old.