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722.6 Transmission Fluid and Filter Change

on the 1997 Mercedes C230

by Kim Langley


There is a lot of hype out there that the mere mortal does not posses the technical skills to change the transmission fluid on his/her Benz and there is a cadre out there saying it's as easy as an oil change. I am of the opinion that it is somewhere between the two. The procedure is more complex than an oil change but certainly within the grasp of the majority of DIY'ers.

Tech Specs:

Tools Required:


1. Jack up the Benz as far as possible [front and rear] and support with jack stands. Benz on flat ground I like to use a 6 x 6 piece of plywood to act as a buffer between the Benz and the jack stand]

2. Good idea to put down a good layer of newspaper/cardboard under the Benz to catch spillage

3. As far as I know the transmission can be drained either cold, warm or hot. I drained mine warm.

4. Start draining with the transmission pan drain plug. It's quite obvious. 5mm hex. You should get about 3 liters of fluid out. After the pan has drained, detach the pan via #30 torx [6 bolts]. There will still be about a half-inch of fluid in the pan so be careful [unless you like tranny-oil baths].

5. You can examine the color, smell of the transmission fluid and get an idea as to the status of your transmission > see the color of money article. Additionally, it's good to note any metal particulates in the bottom of the pan. Clean the pan with a lint-free cloth you don't want to induce any unwanted stuff into the system.

6. Remove transmission filter. It's just pressed into position no hardware holding it in position > note it's location before removing though.

7. Drain torque converter. The torque converter is located forward [towards front of car]of the transmission pan in a sort-of oval housing. Unless the drain plug stopped in the down position, you will have to have someone turn the engine over to rotate the torque converter. Turning the engine over is accomplished by using a 27mm socket on a long breaker bar placing the 27mm on the crankshaft pulley nut and gently rotating the engine clockwise. Since the rear wheels are off the ground- should rotate easily. Obviously, you don't want to break the crankshaft pulley nut loose just rotate the crank which rotates the torque converter.

8. With the torque converter drain plug in the down position use a 5mm hex with an extension and unscrew. You'll get another 3 liters of old tranny fluid out of the torque converter.

9. After everything is drained it's time to install a new transmission filter, reinstall the drain plugs and secure the pan back to the transmission. Torque to 106 inch pounds [not a lot of torque]

10. I found that the transmission pan gasket was still quite serviceable it's a rubber affair and quite well-constructed unlike most typical US gaskets > so I reused the old gasket.

11. The reinstall of the transmission filter was not exactly elegant You get the filter in position, hope it stays attached, and quickly put the pan into position.

12. Ok, tranny drain plug in, torque converter drain plug in, tranny pan attached .

13. Clear-out all stuff under your Benz and lower off of jackstands.

14. Now it's time to pour in new transmission fluid. Obviously > use only the correct Mercedes Benz fluid > .

15. I poured in six liters and took the Benz on a short/medium drive to get the transmission warmed up. I wrapped a rag around the tranny tube > used a long neck funnel and slowly poured the fluid in.

16. With the engine running, car in Park, > use the infrared thermometer and ping the tranny pan the pan should be the same temp as the fluid inside.

17. Unclip the red plastic piece on the transmission cap and remove the cap.

18. Using the MB dipstick tool check the fluid level.

19. This is where the purists' note that only a shop with the special MB diagnostic star-gizmo can perform the procedure.

20. I maintain that if my infrared thermometer says the tranny pan/fluid is at 80degrees Celsius, and the tranny fluid level on the special MB dipstick tool is at the top mark at 80 C, then I am good to go. I have filled the proper amount of fluid. I used 7.3 liters of fluid for the change.

21. It should be noted that the MB dipstick tool reads from the bottom up. That is, stick it all the way in and pull it out, read the fluid level. You will have a good 8 inches of dipstick hanging out the transmission tube overhanging the engine remember it's a tool...not a dipstick.

22. Some of you are going to be griping: Man, I gotta buy a special dipstick tool, a blinking infrared thermometer...a 25 inch breaker bar...too much gingle for this gig. Let me impart my tools-are-free philosophy. It indie shop wanted $125 to do a tranny fluid change and that's with me providing the filter and fluid. So I spent $69.00 for a infrared thermometer and $30 for a dipstick tool.. I purchased the correct tools so I could perform the task correctly so with my labor [$0] and special tools purchase $99 I managed to get the job done for less than what a shop would charge for it.

- Kim Langley

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