Transmission Oil Change                                                                             

We get lots of calls about the cost of the transmission oil and filter.   Mercedes-Benz didn’t explain this very well, so there are lots of different thoughts on the subject.   Mercedes came out with their first electronic transmission in 1996.    They told owners it never needed to be serviced.   They just burnt up and you buy a new one.    (One important thing consumers need to understand.   Because we live in a very litigious society, manufactures are not inclined to admit mistakes for fear of ending up in a Class Action lawsuit.)  Mercedes stumbled around for several years without really telling owners they need to service the transmission.   Finally they ended up saying to service the transmission every 40000 miles.   Then Mercedes came out with a new seven speed transmission in 2005.   Once again they told owners the transmission never needed service.   They forgot what happened to the first version.   In fact, Mercedes was so confident the seven speed transmission was so perfect it didn’t even have a way to check the fluid level.   You guessed it, they all failed.   But not for the reason you would think.   According to Mercedes-Benz, VDO messed up the computer programming; causing the transmission to suddenly go into neutral while driving.   Of course Mercedes and VDO deny everything and have never heard of the problem; but just in case, they made a special transmission computer update.   Just in case the car suddenly lost power while driving.   As of 2008 they got that minor misunderstanding behind them.
But what about routine maintenance?   When does the transmission oil and filter get changed?   And if there’s no dipstick, or dipstick tube; how do you know how much oil’s in it or even add oil?   “Engineered like no other.”   This is where things get a tiny bit confusing.      Officially, the transmission oil can only be changed with a Flushing Machine.   The oil pan comes off and the filter gets replaced every 40000 miles, on some models.   Other models with the same transmission & the same oil, it’s once and never again.   It takes ten quarts of Mercedes own special transmission fluid and a couple of hours of labor.   Without a dipstick or dipstick tube, the fluid is added through the drain plug.   To check the level, the transmission fluid must be at 50C.   The mechanic removes the drain plug and the oil streaming out must be 8mm wide.   If the oil level is high or low by half a pint, the transmission shifts terrible.   It’s not uncommon to bring the car back into the shop and recheck the level three or four times.   Mechanics hate changing the transmission oil.   Some shops have a clever short-cut.   The mechanic drops the oil pan and changes the filter.  He puts the pan back on and pumps 3.5 quarts of transmission fluid back into the transmission.   Done.    But wait… what about the other 6.5 dirty quarts of oil in the Torque Converter & oil cooler?   Well, they charge half as much, so you get what you paid for…. sort of.   What if your car is a “4-matic”?   The Transfer Case has its own oil; did it get changed?   Not exactly.   You just drive it until it burns up.   What about the front and rear differential oils?   Drive them until they burn up.   Or, just buy a new car every four years.   Then it’s the next guy’s problem.