JHZR2
Staff member
I decided to service my 2008 ML 320 diesel with 203k miles. I forget when it was done last, I have the receipt someplace, but I do recall that it was a while ago and since the weather was so nice, it seemed like a good time to try to do it. I will say that I have serviced a lot of the Mercedes-Benz 722.3 and 722.4 automatic transmissions, and they are set up so well that they are a breeze to do, and you don’t get a drip of fluid anywhere.
Boy, did this one make a mess, even though the pan and gasket are generally set up the same, and you drain the torque converter the same way.
Here are some photos of the job:
The transmission requires a pressurized filler. I understand that this is not unique to Mercedes-Benz transmissions, in fact, it seems to be more and more common on a wide range of designs. The issue I really have is that there’s a standpipe that gets inserted over top of the drain plug. On the older transmissions, the drain plug is just removed, and the threaded fitting is much lower down, allowing a more substantial drain of fluid, and a very clean pan drop. This transmission requires you to pull the plug, which drops a few quarts, then use some sort of a tool to remove the standpipe, which removes a few more quarts. This also prevents you from being able to do an easy drain and refill of fluid. And worse of all, it leaves enough fluid in the pan for the final drain to be every bit as messy as any American transmission that doesn’t have a drain in it.
That said, once the pan is down, everything was very clean on the valve body. There was a decent amount of fine black dust on the filter, and on the magnet, but nothing that was large, abrasive, etc..
The filth on my hand is from the removal of the filter, as fluid dripped all over my hand. Stupidly, I wasn’t wearing gloves, as I believe I was on my fourth pair. It’s such a pain to wear gloves and take them on and off.
The pan bolts are somewhat curious, they are aluminum hexolobular design. They’re single use only, and are torqued to a mere 4nm, then turned 180°. I did screw up on two of them, as I had my torque wrench set to 72 inch pounds from another item, and I took two of the bolts too far before I checked my work. But they did back off, and then I torqued them to spec, and it seems OK.
The torque converter is also easily drained, though I was someone surprised upon the refill that it sounded loud until all the fluid was pumped from the pan into the system. Draining the torque converter is common on any of the Mercedes transmissions, and no others that I’ve serviced have a bit more noise at startup, until the convert is full. It was very obvious on this one.
The transmission gets a pressure fill, which works exactly like the factory service manual suggest. You pump in about an extra quart, then start up the transmission, and watch the transmission temperature with a scan tool. You pull the filler in order to let fluid drain out, And when it hits 45 C, and is slowly dripping, you plug it and you’re done.
I filled the transmission with Fuchs Titan 4134, which is on the approved list.
My primary complaint is really associated with the fill process, or more specifically, the requirement to have a standpipe in the filling system, which leaves too much fluid in the pan, and allow a much bigger mess to be made as compared to the older unit. What would’ve been better is to have a fill plug on the body of the transmission, and the drain plug in the pan the same as all the older units. This way one could easily drain all the fluid, easily fill all the fluid, and drop the pen with the greatest of ease without any mess whatsoever. The pressure fill and temperature set fill could still be done.
The transmission shifted flawlessly, smooth and just right. I don’t expect any changes with the new fluid, though it was obviously brown, and has been in use for a while. Now it’s good for another 50,000 miles, or whatever makes sense.
Boy, did this one make a mess, even though the pan and gasket are generally set up the same, and you drain the torque converter the same way.
Here are some photos of the job:
The transmission requires a pressurized filler. I understand that this is not unique to Mercedes-Benz transmissions, in fact, it seems to be more and more common on a wide range of designs. The issue I really have is that there’s a standpipe that gets inserted over top of the drain plug. On the older transmissions, the drain plug is just removed, and the threaded fitting is much lower down, allowing a more substantial drain of fluid, and a very clean pan drop. This transmission requires you to pull the plug, which drops a few quarts, then use some sort of a tool to remove the standpipe, which removes a few more quarts. This also prevents you from being able to do an easy drain and refill of fluid. And worse of all, it leaves enough fluid in the pan for the final drain to be every bit as messy as any American transmission that doesn’t have a drain in it.
That said, once the pan is down, everything was very clean on the valve body. There was a decent amount of fine black dust on the filter, and on the magnet, but nothing that was large, abrasive, etc..
The filth on my hand is from the removal of the filter, as fluid dripped all over my hand. Stupidly, I wasn’t wearing gloves, as I believe I was on my fourth pair. It’s such a pain to wear gloves and take them on and off.
The pan bolts are somewhat curious, they are aluminum hexolobular design. They’re single use only, and are torqued to a mere 4nm, then turned 180°. I did screw up on two of them, as I had my torque wrench set to 72 inch pounds from another item, and I took two of the bolts too far before I checked my work. But they did back off, and then I torqued them to spec, and it seems OK.
The torque converter is also easily drained, though I was someone surprised upon the refill that it sounded loud until all the fluid was pumped from the pan into the system. Draining the torque converter is common on any of the Mercedes transmissions, and no others that I’ve serviced have a bit more noise at startup, until the convert is full. It was very obvious on this one.
The transmission gets a pressure fill, which works exactly like the factory service manual suggest. You pump in about an extra quart, then start up the transmission, and watch the transmission temperature with a scan tool. You pull the filler in order to let fluid drain out, And when it hits 45 C, and is slowly dripping, you plug it and you’re done.
I filled the transmission with Fuchs Titan 4134, which is on the approved list.
My primary complaint is really associated with the fill process, or more specifically, the requirement to have a standpipe in the filling system, which leaves too much fluid in the pan, and allow a much bigger mess to be made as compared to the older unit. What would’ve been better is to have a fill plug on the body of the transmission, and the drain plug in the pan the same as all the older units. This way one could easily drain all the fluid, easily fill all the fluid, and drop the pen with the greatest of ease without any mess whatsoever. The pressure fill and temperature set fill could still be done.
The transmission shifted flawlessly, smooth and just right. I don’t expect any changes with the new fluid, though it was obviously brown, and has been in use for a while. Now it’s good for another 50,000 miles, or whatever makes sense.
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