I have 95 Bronco witha 351, with the E40D auto trans. In November the speedo started jumping up and down, and at hiway speeds the transmission would start to slip.
I changed the speedo sensor (VSS) at the rear axel. That solved the problem for a while.
Its doing it again! I changed the sensor again with no luck this time. I checked the wiring, I checked the sensor. OK!

What else is there? My buddy says to change the computor. I want to get some other ideas before I spend more money on parts I don't need. ($200)

 

i could be wrong, but i always thought the VSS was mounted on the transmission, and the sensor in the rear diff. is an ABS sensor...hmmm, not sure...

 

On those years the VSS and the ABS sensors are the same sensor at the top of the rear dif.

What I would do next is to check for codes...........even if your CEL is not illuminated there will be codes stored......and if you need more help on how to get the codes and what they refer to, I am sure someone here will help out.
I think your truck is OBD I, and if it is you can use a paper clip to retrieve the codes.....I just bought a scanner for like $30....plug and play.

Anyhow......I would check the codes and if I had to pick a direction to look in at this point I would say it could be the MLPS.

use the search

 

Thanks guys, I'll take it to get scanned.

 

If you take it to get it scanned go to a Ford house, or somone with ford equipment. Most places like Autozone have generic code readers that are totally incorrect. You should just buy your own and get in the habit of checking for codes ever once in a while. It's better to check and verify that you don't have any codes than to wait until there really is something wrong.