In this repair we Address a problem with a Jeep Grand Cherokee 2006. It had the problem of randomly dropping out of gearing and going into safe mode meaning it would lock and hold 4th gear and it would also not apply the locking torque converter. The owner was told in the past they would need a full new transmission to fix this problem but this is simply not true. The NAG1 transmission was built by Mercedes these transmissions hardly ever fail mechanically but there electronics especially the electrohydraulic control module often do.
They fail do to the metals floating around in the transmission fluid. The metals cause the open contacts to short out and burn up the 3 speed sensors on the module. It is Easy fix to fix and only takes 3 hours of work. We drop the valve body replaced the module, refit change, and change the filter and pan gasket as well as the electrical plug orings. We then do a transmission fluid flush and its good to go after the codes are cleared!