Can't get my speedo working on my 90 dodge truck. Replaced sensor and speedo with known good units, gear in trans functioning well, changed engine computer as well....what gives anyone?

They get goofy after 130-150k miles on the trucks I've had. Make sure you check all the connections, it helps to have a good wiring diagram. You will see an orange wire in a large harness connector under hood near trans dipstick tube, that IIRC is the signal wire from trans to speedo head. It goes other places too, so diagram is a must.

so it should not have power, how does it get the signal is it magnetic or what? I have traced the wires and ur right its orange with a white tracer.

I can't recall if the speed sensor is pm generator or not.

when everything seems to check out and doesnt work arrgghh