I just stumbled upon this forum a few days ago and I have to say I like it a lot!

I have a 95 F-150 with the 5.8L and E4OD auto trans. The speedo jumps back and forth between 60 and 70mph when I'm traveling at 70. It also does it at lower speeds but doesn't move as much. Is this just a speedo cable or is it electronically controled or what? Thanks for your help!

Tony

 

Normally this is caused by the speedometer cable seizing up, but yours doesn't have a speedometer cable. Your speedometer is electric, so I would check the VSS (vehicle speed sensor) located in the rear end housing. It's on the front of the housing up high.

 

I also have a 95 5.8L w/E40D 4WD trans. My speedo jumps a little between 60 - 70mph, but once I settle at driving speed it stops. It does not do it at any other speed.

 

Cool, I was hoping it wasn't the speedo or PSOM or whatever they call it. I'll try replacing the VSS and see if that fixes it. Thanks!

 

Forgive me for not getting to this right away...

I finally got a chance to mess with this last week. I replaced the vehicle speed sensor (VSS) with a generic auto parts store unit and it actually made it much worse. So bad that it was confusing the transmission and shifting out of overdrive when I was at highway speeds!

I double checked the connections and made sure the sensor was seated correctly and the trans stopped goofing up but the speedo was still going crazy. I took it to a friend of mine who runs a trans shop and he confirmed it was indeed an electrical problem and told me to replace the wires going to the sensor as he has seen this many times before.

I replaced the actual wire going from the VSS up to where it goes into the main wire loom going down the frame rail. I took my time and soldered and shrink-wrapped the connections the way it should be. Unfortunately it didn't change a thing; the speedo was all over the place.

Finally, out of shear frustration, I took the old sensor out and put the original one back in and it fixed it completely! The speedo hold true at any speed and I returned the generic cheeseball sensor.

My friend that helped me diagnose and fix this (he also works as a mechanic) later told me that he came across a technical service bulletin that said the wires tend to break inside the insulation due to body flex and weather corrosion. My friend at the trans shop told me the same thing too.

So, to anyone who has been dealing with the notorious fluctuating speedometers that Fords seem to have, try replacing the wires before the VSS.

Tony

 

Thanks, I've been having the same problem on my 96. It will jump from 65 to 10 and back up from time to time. It only does it for a second, but it's really annoying and sometimes messes with my cruise control. I'll inspect/ possibly replace the wires you mentioned this weekend.

 

i gotta check mine it been all over the place. at first my speedo didn't move at all so i replaced the vss because the old one was all chewed up and now it bounces all over the place. i'm gonna check the vss again (hopefully its not messed up) and the wires.

 

Hello All,
I have just lost power or ground to several things. Mainly no speedo and odometer which causes my trans to shift hard. (1992 150 w/6cyl.) I first thought a fuseable link blew, but I checked voltage to the fuses, which was good.
Also, I lost power at the dome light, the radio, and electric mirrors. No fuses are blown and voltage at all fuses.
I can only think that all these things share a common harness ground wire that has broken or lost connection.

Anyone heard of this before, let me know. Mean while, I'll check the ground at the easiest thing and find out if voltage or ground are present, and go from there!!

 

I have a 96 4.9L with a manual tranny....my speedometer doesn't jump around...the speedo is reading nothing - 0mph just started this morning, was fine yesterday...but there was (for the past 2 weeks) this clicking at low speeds from the left rear wheel. Are the 2 related? what needs to be done? how much? how long?

 

speedometer jumping around