Differential vs. Transmission Speed Sensors

[NORVIN]

What is the difference between Differential vs. Transmission Speed Sensors? I have a 2003 KJ Limited with the 45RFE transmission. Does it use both? My speedometer works after the Liberty has been parked for awhile. It continues to work at highway speed for about 5 miles then jumps around and stops working.

 

[JeepJeepster]

Typically its a bad wiring harness on top of the rear diff. Mopar use to (and they may still) make a repair pig tail to fix the issue.

 

[KJowner]

Transmission speed sensors are used by the Transmission ecu to decide which gear to select, the one on the diff is used by the body ecu for the speedometer and ABS.

 

[NORVIN]

Cool. Thanks guys. I installed a new pigtail and speed sensor. No speed reading at all so new sensor is a dud. Cleaned up old sensor and put it back in. Worked for about 10 miles then stopped reporting speed. Took it out and wiped it off. I saw some very fine metal shavings on the white paper towel.

I also checked oHm readings on both sensors. The old one reads 15.4 M oHm. The new one reads OL.

 

[seafish]

I saw some very fine metal shavings on the white paper towel.

Metal dust particulates are normal, but metal shavings less so ... Maybe time for a rear diff lube change and inspection?

 

[duderz7]

Metal dust particulates are normal, but metal shavings less so ... Maybe time for a rear diff lube change and inspection?

I wanna say there was atsb way back that involved dumping refilling rear diff with "diff"erent fluid because of fouling sensors. But I could be making that up, my memory does weird things now and again.

 

[NORVIN]

Yes. Not "shavings" but "specks"/"particles" were what I saw on the speed sensor.

I drove to a somewhat nearby AutoZone that had the Duralast SU3331 in stock. Drove back and installed it, but the speedometer was erratic. Exchanged it at another AutoZone and everything has been fine since.

I used a Standard Motors S824 Pigtail/Connector and Metra Heat Shrink Solder Tubes to replace the old connector.