For a speed-sensor signal you have a few options. Some automatics have a transmission output speed sensor (TOSS) and others rely on an output speed sensor (OSS) in the transfer case. We had our transmission rebuilt and made sure it had a TOSS installed, and we also installed this Advance Adapters' speed sensor onto the input of the STAK case. 3 The AA piece has the pickup threaded into the transmission-to-transfer-case adapter, so all speed-sensor signals are recorded prior to transfer-case low-range gearing. Thus the tranny always shifts like it is in two-wheel drive. At first we assumed we would need the TOSS to run the Compushift and the AA unit for the factory speedometer, but we found that the Compushift has a reproduced TOSS signal that can be wired into the factory harness to control the speedo.
Here is the new view from the cockpit. There is a B&M temp gauge on the dash keeping track of the 4L80E, the new three sticks controlling the STAK coming up through the floor. The left shifter is for the front output. Push it forward and you have low range, middle is neutral, and back is high. The middle shifter chooses between 5:1 or 3:1 low range, and the right shifter engages the rear output. Unfortunately we got a little excited when cutting the hole for the shifters and had to then go back in and plate over the giant opening we cut. Finally we added a new triple-shifter boot from JB Custom Fab that greatly eliminates heat and noise intrusion to the cab. Also on the floor there is the Compushift display programmer within easy reach and in sight to keep track of the data arriving from the fresh tranny. The red knob on the dash below the gauge is the front axle Posi-Lok activator; see the complete install of that elsewhere in this issue.