Speed Sensor help (what is this thing??)

Hey all,

I have a quick question I am hoping someone can answer for me pretty soon. I just got a new speed sensor for my 91 4.0 Auto w/ NP231 because my speedometer has been on the fritz and the sensor seemed like the culprit. I got a new one from the stealership and when I went to install it I realized it didn't look the same as the one it was replacing (see pictures below)




Does anyone know what the threaded piece coming off the back is? It has an O-ring on it so I am assuming something is supposed to seal on it but I have nothing to put on there. I am just trying to figure out if I can still use it or if I am our a bunch of money since i doubt they'll take the part back.

Thanks, any help would be greatly appreciated.

The part with the O rin looks like that is the part that mounts on your trans. Looks like you have to unscrew the old speed sensor off the o ring part and screw the new part onto the o ring part.

If someone could delete this post, I found the answer to my problem after searching through a couple parts catologues. Apparently the local stealership can't comprehend that my Jeep is a 1991 and not a 1990 despite having said 91 several times.