Locate the Circular, 4-pin Speed Sensor at the rear of the transmission, on the output shaft. This speed sensor has 3 or 4 wires connected to it. We do not have a mating connector to plug into it. So, the only way is to splice into one wire from your system.
The correct wire to splice is the one that's connected to pin #3 on the speed sensor connector. (If you have 2-speed sensors, choose the lower positioned one).
To identify pin 3, unscrew the speed sensor connector from the speed sensor by pushing down and turning counter-clockwise then pull. Look at the face of the connector and notice the tiny numbers, 1 through 4 printed next to each pin. Identify the wire (by color) that connects to pin 3.
On some Volvo Conventional trucks you can Identify the wire color of pin 3 and trace the wire to a junction box mounted on the firewall and splice there. On Most trucks it's best to splice near the speed sensor location.
After identifying the color coding of the wire that is connected to pin #3, trace this wire approx 6" or more upline from the speed sensor. Cut and strip each end of the wire 1/4". Use the heat-shrink, crimp-style connectors that came with the weatherpack pigtail kit.
Plugin the weatherpack connectors, that you just installed, to the Main Cable. Route RCA end of main cable to cab interior, near control unit location.
Shrink tube, crimp style connectors work best for splicing. We use the Weatherpack Pig-tails for splicing. These allow for easy plugin or removal to the main cable. Once the Main Cable has been removed, plugin weatherpack pig-tail connectors to each other to provide normal operation. http://fastertruck.com/products/WeatherPack-Pigtails-XM7WP.html