Mercedes-Benz 7-Speed Transmission (722.9) Service Walkthrough
To ensure long life and peace of mind in your 7-speed (722.9) Mercedes-Benz transmission, periodic service is a must. The 722.9 7-speed transmission comes in two variants that determine the service procedure.
The two variants will be referred to as the red-fluid version, and the blue-fluid version. The red-fluid transmission service intervals are 40,000 miles, and the blue-fluid transmissions need servicing every 70,000 miles. The blue-fluid transmissions began to appear around 2010 model years and can be identified by their blue-fluid, green fill pipe, and deep dimples in the transmission pan. The quickest way to see what you have is by checking the dimples. The blue-fluid transmissions require an exclusive fluid that does not interchange with other transmissions.
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. This pump and adapter are made by AST Tool Company. While this is a somewhat expensive special tool, it would be beneficial to own if you plan on doing more than one 722.9 service. Another option is something along the lines of this. We offer service kits for both transmissions to get the job done.
For this write-up, I'll be referencing a red-fluid 722.9 in an R-Class (V251). I like to do transmission work after the car has been sitting overnight in order to avoid the incessant dripping of ATF that makes the job overly messy. The first step is to pull 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. Do not reinstall the plug at this point. Next, you must knock off the fill pipe that is attached to the drain plug hole inside the pan. This is best done with a small screwdriver and will liberate another quart of fluid.
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. 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. This reduces the chaos that evident when the pan finally comes free.
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.
Drop the filter to release more fluid. Clean up the surface that the pan gasket contacts on the transmission with a lint-free cloth or paper towel doused in brake cleaner. I like the surface to be completely dry before I begin reassembly. Remove the gasket, fill pipe, and magnets from the pan. Clean up the pan and magnets with a lint-free cloth and cleaner. Replace the items you just removed from the pan and be sure the fill pipe has locked into place. 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.
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 its ready. Now you can clean up any remaining mess and check for leaks.
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.