Here at Mopar Muscle we've been drag racing our cars nearly as long as we've been driving, and, like any true enthusiast, we want our race cars to be pure Mopar. If there's one thing we hate to see at the track, it is a two-speed transmission in an otherwise great race car. We've heard the arguments: the two-speed automatic is considered more consistent for bracket racing; it takes abuse well; and it has a ton of aftermarket support, but whether completely aftermarket or not, the two-speed is still a brand-X transmission. The reality is most race applications, which utilize the two-speed automatic, would do just as well, or better, with a properly prepped TorqueFlite. The advantage is one more gear for torque multiplication allowing more leeway when it comes to converter selection, as well as keeping a heavier race car in its peak power range all the way down the track. The 727 can certainly handle a ton of power and is a very consistent performer, as we've shown with our Super-Pro 68 'Barracuda. If your combination is one that overpowers a race TorqueFlite (which for the record takes way upwards of 1,000 hp), you may be in the market for a Lenco or other pure race transmission. If you're like us and enjoy racing your Mopar with as many true Chrysler parts as possible, we'll show you how to build a TorqueFlite to handle your power and maybe even shave a little off your e.t. in the process.
If you follow drag racing history, you know the TorqueFlite automatic, much like Chrysler's A-833 four-speed, has a reputation for strength and durability. The 727 is a relatively simple piece when compared to other automatic transmissions, and its strength is a function of that simplicity. We've put stock TorqueFlite transmissions behind big-blocks pushing upwards of 600 hp and found they not only survive, but perform quite well. Pure race applications, however, will find the weak link of any combination, and the transmission is no exception. Planting 700 or more horsepower through a set of sticky rear tires in a 3,100-pound door slammer will require some transmission modifications. We're not talking about any high-tech machining or super expensive aftermarket parts, just good, solid replacement parts for what we consider the weaker areas of this tough transmission. Our combination is slated for our '68 Barracuda, which races in Super-Pro (electronics) class, as well as seeing some duty in the local Quick 16 races. To be competitive in Super-Pro, a delay box has pretty much become a requirement, so a transbrake valvebody will be utilized for this build. You don't have to use a delay box to use a transbrake, but you have to use a transbrake to run a delay box. We've never been big fans of delay box racing, but when we put this combination together, it ran too quick to race in the foot-brake classes. Not the type to purposely slow our car down, our choice was made for us, so the transbrake and delay box will be installed, making the car more consistent and competitive.
For those of you unsure how a transbrake works, the theory is really very simple. The transmissions valvebody is modified with an electric solenoid, which will actuate the reverse band of the transmission. When the car is staged at the starting line in low gear, the transbrake button is pushed, engaging the reverse band. This basically locks the transmission in first and reverse, and the engine can be revved to the limits of the stall converter or launch rev limiter without moving the car. When the button is released, reverse is disengaged, and the engine's power is all directed to first gear. The result is a harder, more consistent launch, though sometimes at the expense of drivetrain parts.