Run-away truck

I have a 92 f-150, and it is having some trouble in letting me know how fast I am going. The speedometer jumps when ever it feels like it. Also the rear ABS dummy light comes on and off, again when ever it feels so inclined. There is no speedometer cable in place. Speedometer should be getting signal from rear ABS sensor which has been replaced, located on the rear diff. I have a feeling that if I fix one problem it will resolve the rest. So the first problem is trying to figure out the dang ABS system. Did I mention that I hate ABS. Anyways, how can I pull codes to discover a problem with the ABS system? How can I reset the ABS computer? Does anyone have a clue or experience as to what is happening? Any ideas or comments would help out.

This truck has different sensors for the ABS and the speedometer. The vehicle speed sensor (VSS) is located in the transmission near the tail end. The rear ABS sensor is mounted on the rear differential housing. With the speedo acting up, I believe it is a bad VSS. The ABS module also reads the VSS, and that is probably triggering the ABS light.

No VSS, I did go out and buy a VSS and nothing under that truck that resembles the one I bought. The transmission is a Borg Warner. So that being said, is this transmission actually the one that came with the truck? No proof that it did or didn’t.