Transmission not shifting properly?

Hi,

The vehicle speed sensor is the likely cause of the erratic shifting. Have you checked for diagnostic trouble codes? If not, that is where I would start.

Keep in mind, the PCM uses the frequency signal generated by the VSS (and other inputs) to control such parameters as fuel injection, ignition control, transmission/transaxle shift scheduling, and torque converter clutch scheduling. So, if the VSS is off, shifting can certainly be affected.

For F-Series vehicles, the VSS signal is generated by the Generic Electronic Module (GEM). The GEM generates VSS from a speed sensor on the rear axle. I attached a pic below to help locate it.

Remove the differential speed sensor and inspect it for dirt, corrosion, or any damage. Also, confirm the wiring to it is good and not damaged.

Let me know what you find.

Take care,

Joe

See pic below.

Hi,

Were you able to check the vehicle speed sensor I mentioned?

Let me know.

Joe