As stated I have a 1994 F350. Lately it started getting some hard shifting, and as your driving 65-70 some times the transmission seems like it shifts into neutral, the tach goes way up, but if you slow down or manually shift into a lower gear it grabs and goes like nothing happened. Could this be a shift module going bad? The fluid and filter was just changed 600 miles ago. Any help would be appreciated. Thanks in advance

 

Not knowing who changed the fluid etc.,did you check the trans fluid level?