TCI's Trans-Brake Series allows you to achieve maximum torque converter stall and provides for quicker and more consistent reaction times and 60 foot times. This is due to the Trans-Brake action which prevents an engine's torque load from being transmitted through the drive train prior to the launch. The Trans-Brake acts in much the same manner as a manual clutch. Once the Trans-Brake is engaged, the vehicle can neither roll forward nor backward and as you press on the accelerator the engine can rpm as high as the torque converter stall. Once the Trans-Brake is released, the power is transmitted immediately to the rear tires in much the same manner as a manual clutch but with the parts saving advantage of the torque converter's shock absorbing action. Fits Ford C4, 1971 & later with push-in style modulator. Has reverse shift pattern. Pit Stop USAoffers TCI C-4 Trans-Brake Kit 521500 at low everyday prices. Be sure to check out all of our products from TCI Automotive including TCI Automotive Automatic Transmission Valve Bodies.