ML430 Transmission does not engage when shifter moves

I have the following issue with my transmission. The vehicle was running fine then suddenly i heard a bump then the vehicle started to slow down. it eventually stopped and any pressure on the gas pedal was just increasing the rpms without car movement.. the vehicle could move freely if pushed back or forth which allowed me to tow it. I have read all the posts and none seems to be the case i am facing. the vehicle engine start well and everything is normal. No alarms or fault code. The gear shifter moves normal between park and Drive but the low gears d to 4,3,2&1 does seem to be working  (not shown on dash display). When returning to park from R a ratling sound is heard like a relay or solenoid that would not settle.I checked underneath, and there was no mechanical issue with the linkage.I tryed the low range and it change normally but no car movement as well. Please advise on what could be the problem.