Speedometer question on a 97 K3500 gasser

[Tommy Frantz]

Guys,

Why does Chevy run the speedometer signal through a speed buffer module (drac?) on a diesel and use the vcm (vehicle control module) on a gas truck? I'm changing final drive gears on my gas K3500; will I need to get the vcm reprogrammed for the new gears? Who should I send the vcm to to get that done?

Thanks!!

 

[skylark]

The diesel system is like the rest of the Chevy diesel system until the duramax, half assed. It is based off of the obd1 system and really there is little difference between obd1 and obd2 with the diesel. The gas engine is a completely different system for obd2. Blackbear can tune a 97 blackbox pcm.