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.