I have a 1989 R688ST. I recently replaced the transmission from a 9 speed Fuller to a 13 speed Fuller. The original speedometer was cable to the rear of the transmission. The new 13 speed is sensor on the yoke. The new electronic speedometer is five wires: power, ground, dash lamp, and 2 sensor wires. I have good ground and power and I get the display for the speedo. I also replaced the sensor on the yoke. Everything is new. The problem I am having is that when the speedometer is plugged in, it will go crazy, to 45MPH, then to 85, the back to 25 etc. Any help would be great. I can't figure out what I'm doing wrong. I believe I have everything connected correctly.
