Hello,

Recently I have bought an 2003 e53 3.0 diesel with transmission issues. It has GM 4L50E transmission.

Car seems to drive forward normally. Shifts up an down no problem but has no reverse and drives forward when neutral is selected. In between shift from park to reverse car tries to move forward, then stops abruptly. Behaves like if it was in park when throttle is applied in reverse. No transmission safe mode is shown on display.

Diagnostic shown 0 trouble codes in TCM but I am unable to connect to ECM. Also the check engine does not light up when I put key into second position.

I have removed the tansmission oilpan and checked the linkage and manual valve. Everything seemed normal no debree or metal inside, oil was not burned. After that I have removed the valve body and replaced it with one from used transmission that was slipping but was driving forward and reverse. Also replaced the range switch inside transmission. All of this made no change at all and car is behaving the same.

Also I have disassembled the original valvebody. All solenoids were functional no contamination inside. Valves OK. But 3 out of 4 springs in the acumulators were broken into pieces.

I would greatly appreciate any advice on whether should I remove transmission and look for internal problem or there is possibility of this problem being electrical.
There are signs of water corrosion on contacts of tcm but it seem old and car was supposed to drive fine just weeks ago.

Thank you all very much
Best regards Samuel