Man, what a great place to learn. I purchased my SD about 5 months ago. '02 F250 2WD with about 173,000 on it. I have driven it all winter with no issues whatsoever. I have had an issue come up in the last two weeks though. I thought I had it licked, but alas it still looms. Here is my issue. I was driving last week on a lot of melting snow and sand and salt. I noticed that the O/D light started flashing, so I read the forum and learned of some of the issues that are sometimes culprits on the flashing light. I cleaned the position switch on the transmission and then removed and cleaned the speed sensor on the rear differential. No problems for a few days. Then it started again. I thought I better get to a trans shop, but I happened to look at the speedo while I was sitting in the parking space. Sitting at a dead stand still in park, the speedo showed 15 MPH when I had my foot on the brake. Once I let off the brake it went down to zero. Put the truck in gear and drove off. After about 15 seconds of driving O/D light went off. As I pulled up to the stop sign and depressed the brake pedal everything worked correctly. Once the truck came to a complete stop, speedo went back to 15 mph. After about 5 or 6 seconds, O/D light started flashing. Took off from stop sign and transmission shifted from 2nd to 1st after acceleration. Drove about 15 seconds light went off. Then, the whole cycle repeated. I started shifting into neutral after a couple of lights so that I could take my foot off the brake, and that seemed to keep the O/D light from flashing and the transmission works flawlessly. Question is, has anyone had an issue like this? It seems to be brake switch related, but I could be wrong. Thoughts??? This has been an on again off again type issue. No real cause to put my finger on. Thanks in advance.

 

Welcome! Are you getting any codes? Somebody will post schematics for those two circuits to see how they may be related. With the age of these trucks sometimes it's just worn spots in wires touching something it shouldn't. Your in the right spot for answers though.

Good luck!