My 1998 F150 runs just fine. I know that the speedometer was correct before winter. However, over this past winter, the speedometer stopped working for a few days, then all of a sudden it started working again. Only now it is showing the wrong speed. I'm actually traveling a lot faster than what is being shown on the needle. I know this by checking with my GPS. it WAS correct before it stopped working...

Its a 1998 Ford F150 with a 4.6L EFI-SOHC (according to VIN)

I know that there is no cable running it, its all electronic on the back of the instrument cluster. What could the problem be?

 

Did you check the vss gear and make sure it's not damaged?

 

No, I haven't checked anything but the instrument cluster yet. I'm not sure where to start... This truck does not have the cable coming into the cluster for the speedo, it has wires...

 

I not an expert on this, but the 97-98 have a vss gear on the trans that controls the speedometer via signal sent to the gem/pcm which would be the wires up see coming to the cluster. Again, not an expert so my terminology may be off.

 

Yes, that's what I gather, but I think the gear is on the rear differential isn't it? what I don't understand is how it did work correctly, then stopped working, but then started working again but giving the wrong speed...

 

It's either on the trans or transfer case depending on 2wd or 4wd.

Why it stopped working, I can't tell you. Could be something faulty on the computer side of it, or the gear could've gotten jammed up and then broken a tooth when it started working again.

 

Its a 2WD... would be on top of the transfer case? or on the transmission? I've never changed one out and not sure about it...

 

It'll be on the transmission, you don't have a transfer case. It's near where the driveshaft is if I remember right.

 

Thank you. Ill check that out the first chance I have to crawl under it...