1991 Mercedes Benz 300e transmssion problem

Hello,
My 1991 Mercedes 300E will not move in any gear. I raised one rear wheel off the ground and the wheel turned forward in all forward gears and in reverse. With wheels on the ground and in any gear the car makes a very slight forward movement when engine is reved but doesn't actually go anywhere. I disconnected the top line from the transmission cooler and reved engine a bit with transmission in gear and saw no fluid. No fluid has leaked from transmission, fluid is at correct level. Fluid and filter was changed about 5000 miles ago. The problem occured while driving at normal 50 MPH and not shifting up or down. Car holds in park.