Sometimes(not all the time) my ABS light comes on at around 75mph. There is no change in braking power or feel or anything, everything acts the same. I've change the ABS sensor that goes in the differential, and it still does it. There is no more than normal vibration/shaking. and also simultaneously the speedometer jumps up 5 mph. I have 4-wheel ABS.

Thanks

 

Do you have another set of wheels/tires to throw on?

I'm thinking those mudders are putting some bad vibes through your axles into the ring gear / tone ring, affecting the pulses being output from the VSS.

It HAS to be VSS related if the speedo is jumping when the ABS light comes on.

 

+1 Vss

 

What is VSS?

 

The ABS sensor that goes in the differential (VSS= vehicle speed sensor)

which you have already replaced, according to your first post.

It's signal performs two functions, speedometer/odometer and ABS (on the 98-2000's). The only thing left is wiring. You can take the connector off that is under the driver seat and clean any corrosion out of it (big square connector, visible from underneath), then reconnect it with some dialectric grease. It is prone to corrosion.

Look at the wires for any rubs, chafes, broken insulation, etc. back to the sensor itself, maybe clean its connector pins.

I'd still try another set of tires, if you have a set (or an accomodating buddy with another Ranger).

When you replaced the VSS, did you inspect it? Any signs of wear on its face where the tone ring passes by it? Metal shavings, crud, etc? Did the new one seat properly?

Worst case is your rear axle ring/pinion is so worn that it is affecting the VSS' air gap to the tone ring. I'd think you'd either hear that howling or feel the slop.

 

is that box literally under the seat or under the truck below the seat? Yes the VSS is seated properly. There were no signs of wear on the old one, I actually replaced it a few months ago. It has a practically brand new axle on it because the original axle's ring/pinion gear was practically gone, (we figured it would be easier just to replace the whole axle) the vibration from that is what set the old one off. I'll have to check all that other stuff some other time