Replaced transmission on 2010 C300

Morning All,

I have a c300 2010 with about 40,000 miles bought certified from dealer this summer. The car was making a humming noise, took it in about 3 weeks ago and was told that I would have to replace the tranmission because of an issue with the transfer case. They would not give me more explaination as to why this happend to a car that is 3 years old. I called my old mechanic and he says that he has never heard of a transmission issue with a car so new and I should demand some sort of extended warranty beyond the standard 4yr/50,000 miles for the transmission. Looking for some reasons as to why this would happen, do you think the dealer sold me the car with this issue? What other issues may come up because of this problem? Any response would be appreciated. Thank you.

Transfer case implies all wheel drive. Do you have all wheel drive?

I am assuming that a C300 is a Mercedes.
If I am correct, I would hope that this luxury car manufacturer provides luxury level customer service.

I am not sure from your post whether the transmission is being replaced/overhauled under warranty, or if you are paying for it. Can you clarify this important detail?

In any event, …open your glove compartment, take out the Owner’s Manual, and find the contact info for Mercedes Benz of America on the corporate level. There should be a toll-free phone number as well as an address.

Phone them and–calmly, politely, and rationally–explain the situation with your 3 year old, low mileage, “certified” Mercedes, and request good will assistance with the repair costs if you are paying for the overhaul. Hopefully they will come to your assistance so that you don’t have to take out a second mortgage on your house in order to pay for the new transmission.

If this repair is covered under warranty, I guess that there is no harm in asking for an extended warranty on the new/overhauled transmission, but I wouldn’t get my hopes up on that score.

It is a Mercedes 4matic/all wheel drive. The transmission was replaced. My issue is that customer service at the service department was not helpful in answering my questions. I was told that I would not be able to get an extended warranty on the transmission once the car reaches 50,000 miles. My issue is, what if I have another transmission issue then I would be responsible for paying it out of pocket after the warranty expires. And I am not sure what other problems will come about because of the transmission repair, worst case scenarion engine.

If YOU paid for new trans at dealer, YOU WILL get a warranty for that trans. How long? Depends. Some dealers warranty major repairs for a long time. Most general parts, like p/s pumps, alternators, starters might have 1yr/12 k mile warranty. A trans might be 3yr/36k. Was the trans replaced under original warranty? Like, the 4yr/50k warranty?

“I called my old mechanic and he says that he has never heard of a transmission issue with a car so new.”

I bought a brand new 1982 Pontiac Trans Am in late 1981 before I left on vacation. I was about 50 miles from home when the transmission blew apart in the middle of the interstate. I submit this as proof that anything can happen at anytime to a mechanical device.

INFO: Pontiac sent a tow truck out to us…put the family in a nice motel overnight and sent a brand new Trans Am to our location the next morning. The dealership had me save all the gas receipts and paid for all of our vacation gas. The new car was a better color according to my wife so it all worked out. It ran great for the 5 years that we owned it but I never bought another Trans Am…new or used.

To answer your question, many all wheel drive vehicles are sensitive to the diameters of the tires, that is they do not tolerate very much of a difference in the diameters in the tires for very long, and by very long, I mean as little as 50 miles.

Neither you or the mechanic that certified the car can tell if the previous owner had run tires with different diameters for very long, i.e. using an odd size tire or replacing just one or a pair of tires instead of all four.

If the previous owner had a blow out when the tires were about half worn and just replaced one of them, it will damage the transfer case on a lot of AWD vehicles. If the previous owner did not do tire rotations as recommended and the difference in tread depth became 2/32" or greater between the most worn and least worn tire, damage would be done. If the previous owner replaced only two tires due to wear, damage would be done.

Check all four of your tires for tread depth. If they are within 2/32" of each other now, you should not have any trouble with your new transmission. If they are greater than this, then you need to either have the best tires shaved to match the tread depth or the most worn one or buy four new tires.

Be sure to keep up with your tire rotations and alway look for signs of misalignment. I do not recommend getting an alignment (4 wheel on this car) unless there is an issue with tire wear or drivability, but at the first sign of either one of those issues, get it aligned immediately. Also keep an eye on the tire pressure, a severely low tire can also cause a strain on the transfer case.

Assuming the OP has the 7speed 722.9 transmission, I can say from professional experience, it wasn’t Benz’s most reliable design

And that’s putting it nicely

Of course, anybody at the dealership will deny that and claim it’s the greatest thing since sliced bread, because they aren’t allowed to badmouth their own product

I’ve repaired tons of them, both mechanical AND software issues. Unfortunately, it was usually a mechanical issue

I have to completely agree with Keith. You now have a new transmission, on MB’s dime. Give it proper care and feeding, especially in the tire department, and chances are you will be fine. It’s not reasonable to expect an extension of the warranty at this point. But if there is a known problem across the board with this transmission, that could change. We bought a 2008 Nissan Altima new. It has a CVT. It started making a whining noise just before the powertrain warranty expired. I rarely take a vehicle to the dealer for service, but I made an exception in this case. The end result was a new transaxle with some sort of updated internals and an extension on the warranty. Apparently Nissan has has big problems with this and they did the right thing.

Like @NYBo said, you got a new one, they owe you no explanation. I bet a previous owner put mis-matched tires on it. That’ll kill an AWD transfer case in short order.

Are all 4 of your current tires matching in all aspects (including wear)?

Being a former long-time Benz tech, I’m going to be a bit more cynical

I suspect the transfer case failed due to no fault of a previous owner

For your consideration, all the 722.9 transmissions repairs I performed were not due to any fault of the owner

And most of these repairs were needed BEFORE the transmission was even due for its first fluid and filter service

We got a new transmission for our van about 2000 miles before the warranty ran out. There are an additional 80,000 miles on this transmission without any problems.