2000 Rodeo-SLE, orig owner, well maintained, speed-o started jumping around and if cruise control is on when it decides to do it, it's a trip ! I think it's all electronic, I pulled, what I think is the speed sensor which is on the tailshaft of the automatic tranny, 2 wires, no gear deal, is there a way to test this ?

The only way to really test it would be to hook up an oscilloscope or a very high end graphing scan tool and watch the square wave it generates. That's an expensive scope though.