Rearend and Transmission Speed Sensors?????????

[justin146]

My Speedometer started doing some crazy stuff. Sometimes the needle will just go all over the place. Every once in a while when I'm going....say 65...the needle will drop down to about 30 and cause the tranny do drop a gear for no reason. So I went to AutoZone and bought a speed sensor for it. The part that they gave me doesnt go in the rearend as I expected. There is a sensor in the rearend, but the one that they gave me fits into the tail of my transmission. What do each of these sensors do? The one in the rearend appears to be a magnetic pickup while the one for the tranny(the part they gave me) has an input shaft.

 

[MattHarrell]

I think the one in the rear axle is the speed sensor for the RABS. That's probably not the one you're looking for.

BTW, where is that sensor located on the rear axle? I crawled up where the spare tire goes and was looking all over the pumpkin but couldn't find the sensor. I did feel something on the front, top side of the axle but I couldn't see what it was. My RABS sensor is acting up and I'm trying to find it to replace it.

 

[justin146]

The sensor in the rearend is on top torwards the front. Best way to get to it is from the front by the driveshaft. Back onto some ramps and crawl under there. The plug off of the sensor faces the front.

 

[MattHarrell]

Thanks. I figured that's what I was feeling but I was hesitant to unplug it without being able to see it.. I'll have to give that a try later this afternoon.

 

[Robert]

The sensor on the rear differential of '97 and earlier Explorers is the Rear anti-lock brake sensor (RABS). If your speedometer is acting strange, then the one you want to replace is the Vehicle Speed Senosr (VSS) which is located on the transmission or transfercase depending on whether or not yours is 4x4. By '99 Ford uses the RABS as the VSS and did away with the VSS on the transmission/transfercase. I don't know if that occured in '98, but it definately did by '99.