A clean transmission oil cooler is a must. Follow this link for more information: Transmission Oil Cooler Cleaning
Locating pins must be double checked in order to prevent misalignment of the transmission to engine: Alignment Pins
After the transmission is bolted to the back of the engine, make sure that there is clearance between the torque converter and flywheel. You should have to move the torque converter forward into the flywheel in order to bolt the torque converter to the flywheel. If the Torque Converter is pressing on the flywheel after the transmission is installed, remove the transmission and install the torque converter correctly into the transmission, making sure it is in all the way.
722.9 transmissions have an engine wire harness located in an extremely bad place. It is common for these harnesses to be pinched between the engine block and transmission bell housing. This will cause a short and trip the check engine light with an O2 sensor code.
As you can see in the photo below, the harness is on the very back of the engine and is loose. It is very easy to miss it's location and allow it to drop down between the transmission and engine during transmission installation.
We zip tie these harnesses to the Crank Position Sensor harness in order to keep it out of the way. We suggest you do the same.
SUN VALLEY MERCEDES TRANSMISSIONS
11239 iLex Ave. Unit B
Pacoima, Ca. 91331
2006 and up 7 speed transmission information