‘91 E150. Ihave intermittent hard shifting between 1st and 2nd. Also when I get to third it almost immediately goes to fourth causing a bog down, is that OD? The dash switch for the OD is broken, has been since I purchased. Half the time it shifts smooth as can be, then wham! I have done a fluid/filter service. The IAC, TPS and O2 sensor have all been changed, just for FYI. I have a mechanic telling me I need a new transmission. When I asked him about changing the MLPS sensor he seemed unaware that it existed. Am I grasping at straws thinking it might be that part instead of an entire transmission? Also the trans fluid is still clean and not burnt etc., the service was done approximately 3,000 miles ago.