A bit of history to start.
Last fall the truck (info below) wasn't shifting gears so I took it to Aamco and there was water in the tranny fluid, so they rebuilt the transmission, installed a new rad for the tranny oil, and replaced the vehicle speed sensor.
In January it started again with the speedometer either not reading at all or jumping erratically at low speeds, so that the transmission wouldn't shift. Aamco said the battery voltage was low and the VSS acts up at low voltages, so now the truck has a new battery and a new alternator. Things seemed okay for a while, but now, every once in a while, when the truck accelerates from a stop the speedometer won't move, and then at about 20 -30 mph it starts to work, and the transmission shifts.
My only guess is a bad connection somewhere between the VSS and the engine computer, and maybe I should run new wires between them. But with only a Haynes manual I have no wiring diagrams to follow.
So, any thoughts as to a solution? I'm open to any ideas
If you think it's wiring, has anyone tried alldatadiy.com? Are their wiring diagrams worth paying for a subscription?
Overall I'm not impressed with Aamco so I'd rather not go back there.