1995 ford F150 5.8-liter-automatic overdrive. When speedometer and odometer stopped working, truck began to shift very hard. Any ideas?
Check to see if there any trouble codes stored in the computer memory.
If no trouble codes then the problem could be a bad PSOM (programmable speedometer/ odometer module).
To test for a faulty PSOM, unplug the vehicle speed sensor located in the rear axel and recheck for the drivability symptom to be present when moving away from a stop. If the symptom is no longer present, the PSOM located in the cluster assembly is the cause of the condition.
The PSOM converts the analog speed signal into a digital signal and sends it on the way to the PCM for a vehicle speed input. If this signal is faulty then the Speedometer assembly needs to be removed and repaired at your local Ford dealer.