I know someone is going to think this is prob a dumb question but what is a trans brake and what exactly do you use it for?the dumbest question is the one not asked right!

 

A transbrake is a drag racing item. It's a specially modified valve body plus a few other internal transmission modifications.

What a transbrake does is to lock the transmission in 2 gears at the same time. Usually first and reverse. When the transmission is locked, the engine rpms can be increased until the converter stall speed is reached and the car won't go anywhere. The vehicle's brakes can't hold back the torque produced by the engine but when a transmission is locked in 2 gears, there's no power getting to the wheels.

When a transbrake is released, the hydraulic fluid is quickly dumped from the reverse circuit and the car launches forward at high rpm in first gear.

A transbrake can be thought of as a clutch for automatic transmissions with high stall converters. It allows you to launch the car at higher rpms where the engine makes it's most power similar to doing a high rpm clutch drop. The amount of rpm you can launch at depends on the true stall speed of a torque converter.

My torque converter will stall to 5700 rpm on the transbrake. I can easily hold the car back at 3000 rpm with just the vehicles brakes. If I want to launch at a higher rpm, the transbrake allows the engine rpms to go as high as the converter's stall speed. Using a 2 step allows me to set the launch rpm I want.

Using a transbrake puts a huge shock load on the driveline just like using a clutch. Small u-joints, driveshafts and diff gears can easily fail from the shock. When I installed the transbrake in my car I also had a 3" x .083" wall steel driveshaft made with 1350 series u-joints. At the same time I pulled out the 7.5" 10 bolt and installed a 9".