While coming back from trailer trip my F250 suddenly went out of 'Cruise' and then the ABS (Anti Skid Braking System) problem light came on. While I was considering what could be wrong, the Service Engine Soon light came on. Things were going south in a hurry, but it was still going down the road. After a pit stop, the transmission started to shift very rough from 1st to 2nd, and the speedometer stopped working. After getting back up to highway speed the speedometer worked again, until the next time I had to use low gears.
The problem was solved with the installation of a new "Speed Sender" unit on the differential. It's located on top of the differential, and is held in by one bolt. It was easy to do. The old one's magnetic sensor end was covered with fine metal dust, which may have been the cause of the problem. I'll never know as I put on a new unit from the dealer ($32). I erased the Service Engine Soon light by disconnecting the negative battery terminal while I was doing the work. On restart everything worked as it should. I decided to change the differential oil and add the friction modifier , which ended up costing me $75 at Checker Auto; more than the part.
If any of you guys are having rough shift issues with your Fords , ABS lights, or mysterious speedometer problems, you might try this.
The unit sends a signal to the computer on the truck and tells it when to activate the ABS, when to shift gears, and what to display on the speedometer.
The guy at the parts counter at the dealership didn't even have to use the book when I told him what I wanted. I think they sell a lot of them. I'll bet a lot of people have had a 'new transmission' installed over this problem.
