For the benefit of others that may experience speedometer issues I will relay the details of the resolution of my troubles.
I purchased my truck with the speedometer not functioning (no speed indication or odometer incrementing). Two of the aftermarket service manuals I consulted didn't even address the electrical elements of the speedometer. After receiving the factory service manual I ordered, I began the evaluation of the problem as follows:
Removed the speed sensor and tested per the service manual, connect a volt meter and spin the sensor shaft as fast as possible by hand - should see at least 0.5 volts AC. The sensor tested ok rotating in both directions.
Removing the instrument cluster and connecting a volt meter to the appropriate points on the instrument cluster connectors with the speed sensor reinstalled resulted in very erratic volt meter readings in the millivolt range with forward movement of the truck, and erratic readings in the volt range with reverse movement. Further examination of the speed sensor indicated a possibly excessively worn pinion gear on the drive shaft of the sensor. Replacing the pinion gear resulted in appropriate voltage readings at the instrument cluster connectors, but still no appropriate operation of the speedometer.
Ordering, and installing a speedometer head (which was a unit also including the odometer) resulted in a functioning speedometer, and odometer. :-]
While the entire operation admittedly took me longer than an experienced service tech, and likely cost more if you factored in my time, I did enjoy the challenge and opportunity of learning something.
Louis
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