I replaced my tranny speed sensor to try to fix a shifting issue ( Not shifting up)as well as speedo not reading at low speeds. it helped neither does the rear diff speed sensor have an effect on both? hooked up code reader no codes showing.
any help would be GREAT!
Thanks

 

I would think the rear sensor is for the speedo and the rear tranny would be for the tranny computer

 

The tranny sensor has to be for the shifting otherwise the truck wouldn't shift at the right rpm when in 4 lo. The rear sensor goes to the antilock module first and then pulses come out of it and feed to the pcm. The pcm does some math on the pulses and computes the speed which is then fed via the ccd bus to the instrument cluster. Try the built in test by holding the trip reset button while turning on the key. Also check the connector at the antilock module. It has a special release kind of a pita.

 

What is supposed to happen?