UGH! Can someone explain the purpose of the 3 sensors that may or may not interact with the e4od, and explain if they go bad or the wiring goes bad.

The sensors I know of are:
Rear Diff speed sensor
Throttle position sensor
Manual level position sensor/Transmission Range sensor.

 

Are you refering to the 89 model in your sig? If so the sensor in the rear end is an ABS sensor and has nothing to do with the E4OD. That sensor was incorporated into the speed sensor and E4OD in the 92 year models I believe. The FPLS tells the transmission how hard you are mashing on the throttle and uses that info to determine shift points. The MLPS tells the transmission which position you have the gear shift lever in. The tack sensor tells the trans how fast the engine is spinning and the speed sensor tells the trans how fast the truck is moving. All these sensors work together for the trans computer to determine shift points.

 

Actually on your 89, the sensor for vehicle speed should be mounted right where the speedo cable comes out of the transmission.

A couple wire plug into that to give the transmission computer the speed info, VSS.

The VSS was moved to the rear axle in the 1992.5 trucks when the speedo went electric instead of cable driven.

 

My 91 has the VSS in the rear end!

-Enjoy
fh : )_~

 

Mine did too.

Man, did I hate that transmission.