2002 Explorer Sport Trac noise and speedometer drops

[melanie26taylor]

I have a 2002 Explorer Sport Trac. It started making a noise when I get to about 45 or so, sometimes. To me it kind of sounds like the motor is rushing but the tach is on 1. The speedometer drops to 20 and the noise continues until I slow down below 20, then I can take off again with no noise. It does not do it when cold or the first 20-25 minutes of driving. My mechanic's first guess was the speedometer cable but it doesn't have one. He said it isn't a metal sound like a bearing, more like plastic or similar noise. The only other symptom it has had is a grinding type noise when I shifted into reverse on an uneven incline, once, added a little tranny fluid and never happened again. It has 100,000 miles on it, I have only had it about 5 months and 5,000 miles or so.

 

[koda2000]

Your speedometer is fully electronic and is run by a sensor located on/in the rear differential (VSS - Vehicle Speed Sensor). The sensor itself has no moving parts and therefore can't make a noise, however the sensor get's it's signal from a reluctor wheel which is pressed onto the differential's ring gear carrier. I've read about this wheel coming loose and causing noise and intermittent speedo reading. I don't know if this could be your problem, but in order to check you'd have to remove the rear diff cover.