The LS1 computer uses the speed input from the T56 & 4L60e transmissions for a variety of reasons including speed signal output to the speedometer, cruise control, lean cruise, idle strategies and anti stall strategies. If you've ever been in an LS swapped vehicle that stalls when coming to a stop, chances are that's due to a lack of speed signal input. The older GM boxes such as the TH400, TH350 & Powerglide units contain an output for a mechanical, cable driven speedometer but no provisions for an electronic signal. This device simply screws into the existing cable output and plugs into your LS harness.
There are two variants available;
BOLT THRU - If you are using a cable driven speedometer. Great for if you've implanted an LS into an older vehicle that uses a cable driven speedometer.
STANDARD - if you are NOT using a cable driven speedometer. slimline version used when you are not using the mechanical output on the transmission or if you've TH400/350/Powerglide converted your VT-VZ commodore
Recalibration of the speedometer in the ECU is required!!