What is the purpose of the ring gear looking item inside the rear differential on a '98 Dodge 4x4 Cummins? and is the electrical connection on top of the differential part of it?

Thanks

It's probably for ABS or might be the device to determine speed for your speedometer. The sensor connection you see would be part of it. I've seen them used for both purposes. I'm just not a Dodge guy.

Umm-didn't think about a speedo. It doesn't look like the electrical tab goes through the housing, can't see it has anything to do w/abs. Son had to replace the rearend so he went to a junkyard and obtained one, and so no one knows what this deal is. Looks like mopar parts call it a sensor ring. He likes to treat this truck like his K-whopper, and haul ungodly loads, hence scrapped rearend.

If the truck has ABS, which it's bound to have at least rear ABS, it is going to get the signal input from that ring. It proves feedback as to whether the wheels are locked in a braking situation. If the wiring is going into the housing, you can bet it goes all the way through. An easy way to tell what it is would be to disconnect that sensor at the differential and see if the ABS light comes on or if the speedometer works.

Maybe a diff lock? I would think MPH sense would come from the tranny somewhere, I really dont know just a wild guess.

After much consideration and marticulation and speculation, I've arrived at the conclusion that I just don't know what it is, but am confident that some day in my travels I WILL encounter a wise man that can enlighten my pitiful lack of knowlege.

Now all I gotta do is just remember the question!!

Old school the speedo gets its readings at the transmission. Today I would *Guess* it's still the same. ABS came about after my time, another guess might be traction control. If it was an option on that model, could be the harness is there, and the hook up under the dash isn't, if you don't have it installed.

It's the rear wheel speed sensor (wss). The VSS is no longer used for Dodge trucks 1998 & later.
The various modules that require speed input share this signal.