ML320 Transmission Fluid/Filter Change

[Jim Grillot]

I changed transmission fluid and filter in a 98 ML320 yesterday. The following observations and comments might help other members who are thinking about doing the job. Overall, it's an easy job. If you can change oil in your car, you can do this job.

The truck has 56,150 miles on it. The driver is conservative. The fluid was coffee color. I don't know if the brown color is from deterioration due to operating conditions in the 722.6 tranny or because the red dye in the fluid is unstable. There have been enough comments in this and other forums about 722.6 transmission failures to make me believe that "sealed for life" means until the transmission dies, not for the life of the car or truck. The smart money seems to be on changing the fluid and filter instead of running the old fluid to the point of transmission failure.

I drained 3.7 liters from the oil pan (including residual fluid which won't drain from the screw plug) and 3.7L from the torque converter. Eight (8) L will handle your refill needs.

Not all the fluid will drain from the oil pan because the weld nut that the plug screws into is pretty thick. Bring the oil pan down level or you will have a mess on your garage floor. Or maybe on you.

You might want to get a large piece of cardboard from a refrigerator box or mattress box and put it on the floor before driving the vehicle into the garage. When the job is over, just roll up the cardboard and throw the spilled transoil away. Sure does make the cleanup easier.

The filter is held in place by the pan. There are no attaching screws. To remove the filter from the valve body, pull straight down. To install the new filter, lubricate the o-ring on the filter neck and press into place. There is a tab on the filter top surface which fits into a slot in the valve body. Use new seal rings on the drain plugs. The seal ring part no is 007603 010100.

I made a dip stick from a length of plastic-covered Bowdin cable from a dead lawn mower. I used a triple-square file and made notches in the plastic cover for full-hot and add-hot. The full-hot level is 65 mm from the tip. The add mark is 54 mm from the tip. A conventional metal tape-type dip stick won't work. The fill tube has bends in too many directions. MB has put out a bulletin advising its techs to ensure that the transmission is filled all the way to the full-hot mark and not short of it.

[Steve Clark]

Best real-world description of the "lifetime fill" ATF to date.I had the C32's gearbox serviced @ 30k miles;wasn't unusual in appearance (still looked like red ATF),but it was getting tired.
Thanks for the dipstick info.Am I correct in understanding that the measurement is innage (from the bottom)?,instead of outage from the top?.Also,what was the dipstick's total length?.

[Jim Grillot]

Correct. You are measuring innage. On the 98 ML320, the distance from pan surface to top of the fill tube is 34 1/2 to 35", depending on some variables.

I stuck the transmission (hot) before changing the fluid. The measurement was 35" from pan bottom to fill tube top, and the fluid was exactly on the full mark.

I talked to a tech at the dealership about 722.6 transmissions and lifetime fill. He related that when he went to school on the 722.6 and was told that it was a liftime fill unit, he and the other techs in attendance were extremely skeptical.

[vince]

You can buy the "official" dipstick from the dealer. It doesn't cost much, but is long enough for all the installations of the 722.6 transmission. It has the standard plastic end you see on later M/B dipsticks. I serviced my E430 at 37,000 miles. The fluid looked fine. There was no wear material in the pan.

[Jim Grillot]

The official dipstick is around $ 38, which is more than I wished to spend for a one or two time use item. My home-made dipstick is 51" long, so about 16" hangs out of the fill tube. (Also, I like to make my own special tools.) Here is a quote from another forum member who owns a factory dipstick. "It isn't the greatest design as the soft plastic tip can be inserted forcefully enough to make it deflect sideways and not give the proper reading."

The important thing is the location of the marks: 10 & 21 mm for 25C and 54 & 65 mm for 80C.

At 56,000 miles, this ML's ATF was dark brown. :( :(

[vince]

Not to be argumentative, but I paid nowhere near $38. Anyone who can break off the plastic end, which is not soft, but the same material as the engine dipstick end, shouldn't be working on their car, IMHO. I make a lot of my own tools, but I reserve that for tools where the expense outweighs the investment of my time.

[Jim Grillot]

The price I mentioned earlier was off the top of my head and was high.

The dipstick part number is 140 589 15 21 00, retailing for $31. With a discount, sales tax and shipping, it would have been about $ 32 delivered to my door. For $ 32, I can drive up the street and get a plastic-covered Bowdin cable off a junk lawnmower. Especially since I know the dimensions to the fluid level marks.

[vince]

The part number is correct and I paid $18 at my local dealer. Also, my dealer shop foreman tells me that the distance between the marks is the range in which the level should be at the given temperature, not the "add" & "full" marks per se. In other words, as long as the level is at or between the marks it is OK. One point that is being missed in all this is temperature. In order to check the level properly, one must establish the fluid temperature. This can be done with a scanner on the ECU or a probe down the dipstick tube connected to a DVM. Alternatively, it can be estimated with an infared temperature scanner scanning the bottom of the transmission oil pan. Short of these methods one can drive the car a given distance and measure the fluid level before draining. After refilling, drive the same route. Presumably, fluid temps should be close and the level should be close. In any case, the temperature of the fluid can have a significant effect on the level, as can be seen by the 44mm difference between the 25 and 80 degree marks. One other note - there may be a difference in the fluid quantity from application to application. I drained 8.5 quarts from my E430 and it took exactly that to achieve the same level at the same temperature.