Auto Transmission & Brake

So starting with what a trans brake is, is basically a custom valve body with an electronic solenoid that is used to mechanically lock first and reverse together, binding the transmission in order for it to not move. So once you apply the solenoid, it locks the transmission up, the truck doesn't move, and then you can spool up. Once it's up on boost, you let go of the button that is commanding the solenoid to be open, locking it in between first and reverse, that releases, and it goes back to being in first gear, and you go down the track.