Here's a thinker for all of you guys.. I have a 1995 f150 5.0, 4x4, 5 speed manual. My speedometer goes absolutely crazy when I get past around 40. And it only gets worse the faster I go. I tried changing my speed sensor. No luck, tried putting a new speedometer in it. Still no luck. It does alright around town at just 25-30 mph. but past there it just bounces back and 4th by anywhere from 10-25 mph off from what I'm actually doing. Any ideas???????

 

Well.. If it's not the speed sensor and it's not the gauge... It's the wiring! Everybody's favorite. It runs down the driver side frame rail.

 

As said wiring gets brittle from sensor back a few feet. It might have a bare spot grounding out.

Also abs controller can cause problems. It's a black box behind glove box. I unplugged mine because it caused same problem your having.

 

So if that's my problem would a new box fix it? And how do I repair the wiring? Do I have to run new wire from the sensor back to a good spot maybe?

 

It's easy to test the box, unplug it and see what happens takes five minutes. Most of the folks with bad wiring could see problem, just trace it from dif and look it over.

 

So I can unplug the box without causing any permanent damage? Stupid question I know.

 

And what can I do if the box is the problem? Can I just grab one out of a scrap yard?

 

Won't hurt to unplug. See if that's even the problem first.

 

There are a couple of boxes behind here. Which one is it? And would this cause it to bounce worse the faster I drive?

 

So I unplugged the box, and it's tons better. But it still bounces a little bit and messes with my cruise control. What could the problem be now?