I'm a little confused here. My trans has an electric shift valve body, and you have to push the button to back up. But if you are in low gear, it doesn't change the throttle peddle at all. In other words unless you step on the gas the rpms never change. Must be the way the MSD is wired that causes this to happen. My trans brake button will come on anytime i push it however it does not lock up in high gear (PG) I did have a manuel turbo 400 that would come on and i did accidently hit it one time, it wasn't funny at about 100 ft. out. That why i now have my trans brake button behind the shifter and no where close to the steering wheel.
JMO
Zip.