Mercedes Transmission Fluid Change

Mercedes Transmission Fluid Change

Here is another critical service that I would like to see people do more often. I knew a guy that rebuilt transmission for a living and I asked him. "What is the number one thing people can do for their transmissions?" He said that if people changed their fluid like they should, it would put him out of business. Hmmm food for thought. Well lets get that old fluid and filter out of that transmission.

Please remember to recycle all your used fluids at an appropriate recycling center. Be mindful to not spill or splash fluids on yourself, others or the ground. Also as a safety tip please remember anytime you are working on, around or under your car, to wear safety glasses and secure the car with wheel stops and approved jack stands!

Depending on the model, you may of may not have a drain plug but most do I believe. It takes a torx head socket. So if you don't have one go buy one, they are cheap and you don't want to ruin the bolt. Just drain into a suitable container.

A word on draining the torque converter: You can do it on the Mercedes, however in the pictorial I just stick to the basic fluid and filter change. Even if you drain the torque converter, there is still LOTS of fluid in the internals of the tranny. The only way to get 100% of the fluid out is to have a fluid exchange machine hooked up to the car. This machine will by pressure, push 100% of the old fluid out of the entire transmission circuit. The machines are only around $3k, but you can get it done for about $100.

When you reinstall the drain bolt, there will be a new washer in the kit, so replace it now.

Clean around the pan where is fits the transmission body before you remove the pan. Six bolts hold the pan on so just remove them.

Here is what is under the pan. The filter and valve body assembly. DO NOT use a cloth or rag to wipe anything during this pictorial, except the outside of the pan. YOU WILL get lint on the valve body and then you TROUBLES are just starting. Use clean paper towels only on the inside of the pan. Do not even touch the valve body or wipe it off. If you don't want tranny fluid in your hair, then let if finish dripping. Lint will destroy a tranny in short order. Don't ask me to explain why, just trust me on this. Even Mercedes goes to great lengths to warn you in the service manual about this. Heck they only want you to wipe the dipstick with leather!

Three screws hold the filter to the valve body. They are fairly long and fluid will go all over your hand and arm if you were impatient like me, not letting it drip long enough. Heck that's why they make paper towels, right?

Install the new filter, noting that the "mouth" points toward the front of the car. Snug the three screws down to seat the filter on the valve body.

I use a de-greaser and water in cleaning the pans when I do it. Just keep in mind the pan inside must be completely dry before installation. I let it dry for about 30 minutes in the sun. Also install the new pan gasket on the pan ridge. DO NOT USE ANY GASKET SEALER AT ALL. The Mercedes tranny pan needs no sealer or any other additive to work. If you do it will probably LEAK.

Refill with your favorite brand of Dextron ATF fluid and check for leaks. I believe it took about 4 quarts to refill this tranny. The longer you let it drain, the more fluid you will have to replace.