I have an '07, which is on a '06 Chassis, a T1N Sprinter model, 5 cylinder. The transmission IS the weak link in this vehicle. It needs all the help it can get. I installed a deep aluminum pan to add about 2½ qts fluid capacity, and also added a transmission temp gauge. I am planning on adding a cooler as the temps climbed a little higher than I liked the other day on a trip.
Quite honestly the fluid needs to be changed about every 20 thousand miles. Mercedes started out recommending 80K, then 60K finally 40K and that is for a regular van. I'd cut that in half for a heavy motorhome. Fluid change should include the torque converter, which has a drain plug, will take 8 qts for a normal pan. Fluid level is tricky to set, you need to buy a dipstick, the dipstick is a TOOL and not intended to, nor can it, be left in the transmission. You check the fluid level and cap the tube when done.
You need to use the proper spec fluids or you WILL have problems. Transmission fluid, their is only about four different ones available, The OEM Mercedes fluid, the Mopar Sprinter/Crossfire fluid, Fuchs 4134, and Shell ATF 134. Use anything else and you can expect transmission problems or failure.
Follow motor oil specs too. Mobil I European Car Formula is most commonly used in the 5 cyl and has the proper approval specs on it. Valvoline also makes an oil with the proper specs.
They are quirky at best and somewhat underpowered. The door locking system will drive you nuts. NEVER EVER lay the keys down in the vehicle, keep them in your pocket at all times. You will never know when the security module will decide to lock the doors on you. Drives me nuts. If one door is unlocked and the others locked, you gotta unlock first, before locking, or it will not lock the doors.
If a brake light bulb burns out, the cruise control will not work, and other things will work strangely. Lots of weird stuff. The list just keeps getting longer.
Edit: forgot to add, Mercedes says this engine is to be operated on diesel that is less than 5% bio, thus pumps that have no bio labeling. If the pump has a 5% to 20% label, do not use it. This is most of the large truckstops such as Pilot and Loves. Buy fuel in places that move a lot of diesel, the fuel filter is marginal and really doesn't do much of anything about removing water.
Edit #2: I bought this in part because I was not willing to have a vehicle with single digit fuel mileage. So far I have been impressed. Trip from south of Atlanta to Huntsville AL Space and Rocket Center, was 18.0mpg, The return I went the long way to stay on interstates, I-65 to Bham and I-20 to US27 south, and got 17.6 on the return as I was doing a little faster speeds than the stop and go that I encountered from Anniston north, and I-65 is quite a bit of up and down hill. Stayed in 4th most of the time at about 60mph, hard on the transmission shifting in and out of 5th all the time.
Charles