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To ensure long life and peace of mind in your seven-speed (722.9) Mercedes-Benz automatic transmission, periodic service is a must. Many manufacturers, including Mercedes, claim that their transmission fluid is for life, but that's simply not the case. Instead, follow this service procedure to keep your 722.9 happy and healthy for hundreds of thousands of miles to come. 

 

722.9-Equipped Mercedes Vehicles

I'll be honest; it's a really long list. Over a decade of service in all sorts of models, the 722.9 was the workhorse of a generation. Luckily, our Mercedes Expert Danny Kruger put together the whole shebang in our 722.9 Transmission Guide, which you can jump to by clicking here.

 

Which Mercedes-Benz 722.9 Transmission Variant Do I Have?

It wasn't long after the 722.9 was introduced that Mercedes had an updated version ready for the public. The update became the 722.9 "Plus" model, and although very few refer to it as such, it contained a handful of changes that required a change in fluid. The changeover occurred in June of 2010 without much of an identifier within easy access to any owner. Before replacing the fluid and filter, you must have the right fluid on hand.

The quickest way to see which variant you have is by checking the dimples on the transmission pan. Early non-Plus red fluid models have a slightly shallower pan than the later variant, so their four dimples are very small. Later blue-fluid variants have deeper pans and bigger dimples. Other differences include their fill-pipe colors and their service intervals, the latter being 40,000 miles for red and 70,000 miles for blue.

Mercedes 722.9 Transmission Pan Comparison

 

What Do I Need To Service A Mercedes-Benz 722.9 Transmission?

The trouble with the 722.9 transmission is that servicing it can be a hassle because it does not have a dipstick or fill tube. It must be filled from the drain plug with a special filling pump and pan adapter. While it's a somewhat special tool, it'll pay for itself if you plan on doing more than one 722.9 fluid replacement. Once you've figured out how you're going to fill the transmission, grab the service kit that matches your transmission. We offer service kits for both transmissions, which you can find here:

However, for those with the early transmission, we offer an update kit. The 722.9 Plus filter and deeper pan have proven to keep the fluid cleaner and cooler during regular operation, meaning better longevity for the transmission's moving components. You can find that here:

 

Mercedes-Benz 722.9 Transmission Service Procedure

Although this walkthrough features images from an R-Class (V251), the general procedure is identical between the transmission variants. As a general tip, let the car sit overnight so that all of the transmission fluid drains into the pan and filter.

Step 1: Drain the Transmission

The first step is to remove the drain plug and drain the contents into an appropriate container. You will be emptying about five quarts of fluid, so be sure your container is large enough. A replacement drain plug is included in the service kit, so throw away the old one. 

Mercedes 722.9 Transmission Service Next, knock off the fill pipe that is attached to the drain plug hole inside the pan. Use a small screwdriver for the best results, and be ready for another quart of fluid to spill out.

 

Step 2: Remove the Drain Pan and Filter

Some cars have a wedge-shaped bracket that covers the rear of the pan and/or a bracket that holds the O2 sensor connectors. You must move these out of the way, or you will surely roll the pan gasket during reassembly—seriously, ask me how I know about that. Then, remove the six E10 Torx screws and drop the pan. I like to remove five screws and hold the pan up with my hand when removing the last screw to carefully take down the pan.

Mercedes 722.9 Transmission Filter

After dropping the pan, look for any large metal shavings or chunks to gauge the health of the transmission. The magnets in the pan will probably look like small Chia Pets under normal conditions. Spiny sea urchins exist in damaged transmissions. Also, give the fluid a sniff to identify if there's any burning occurring. ATF naturally has an oily odor, so don’t confuse that with a burnt smell. It will be pretty obvious if it’s burnt.

Lastly, drop the filter. Doing so will release the last bit of fluid during the job. Clean up the surface that the pan gasket contacts on the transmission with a lint-free cloth or paper towel doused in brake cleaner. 

 

Step 3: Install the New Filter and Pan

Remove the gasket, fill pipe, and magnets from the pan. Clean up the pan and magnets with a lint-free cloth and cleaner and place them in the new pan. Then, take the new filler pipe and press it into place on the pan. 

Mercedes 722.9 Transmission Oil Pan

Install the new filter and pan. At this point, make sure you don't forget to replace the transmission pan bolts! They are one-time-use aluminum bolts that are designed to stretch. Don't over-tighten these because they do break easily.

 

Step 4: Refill the Transmission With Fluid

Using a filling pump, add five quarts of fluid, but don't remove the filler from the pan. Start the car and shift from park to reverse, to drive, and back to park while holding the brakes. Remove the filler and let the fluid drip into a catch pan with the engine running. If no fluid drips out, add another half quart of fluid with the engine still running. The fluid level is set by the fill pipe you just replaced. The fluid is supposed to be 113°F before you're supposed to put the drain plug in, but I usually just feel for a warm pan with the back of my hand. It should take about five minutes before it's ready.

At this point, you can clean up any remaining mess and check for leaks.

Just like that, your 7-speed Mercedes-Benz 722.9 transmission has been fully serviced. Like everything else we sell, the transmission service kits come with our Lifetime Replacement Guarantee. That means that when you do this all again in 40,000 to 60,000 miles, we have you covered. If you have liked this walkthrough, be sure to keep reading the DIY Blog and subscribe to our YouTube channel!


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Written by :
Greg Duffield

Greg Duffield is a Mercedes-Benz Master Technician from the Portland, OR area. Because keeping a high-mileage 450SEL and ML350 on the road is not enough, he is always interested in another old/cheap car project.


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