Intermittent speedometer failure, need help.
1998 Ranger sport 4x4
Electronic controlled transfer case
My speedometer functions most of the time, but on occasion the needle will just go dead for a mile or so. I cannot find the sensor responsible for the speedometer. Auto parts stores have speed sensors in stock, but I don't know where it goes (apparently nobody else does either). I am at a loss.
Some have told me that the ABS sensor in the center of the rear differential provides information to the speedometer. To test that, I unplugged the ABS sensor. The ABS light came on, but the speedometer still functioned.
Some have said that there is a sensor on the output of the transmission or the transfer case. There is no sensor in either location. I disconnected the wire harness (the only wires leading) to the transfer case, and the speedometer still functioned.
I disconnected the back-up light sensor near the shift lever just out of curiosity. As expected, the back up lights stopped functioning and the speedometer still worked.
I can find nothing else to try in the vicinity of the transmission, differential or transfer case. I have called the a$$4@!3s at my local Ford dealership, and some (more friendly) out of town dealerships, and have not gotten an answer that solves the problem. What am I missing?