For our build we'll be using the TCI (pN 121900) transbrake valvebody, as well as several other trick parts to provide our car with a race transmission that will be dependable, consistent, and rugged. The TCI valvebody impresses us with its heavy-duty solenoid and solid construction, and will give us the fully manual reverse shift pattern that we need. TCI also offers this valvebody with a "safety neutral," which is an additional neutral position after third gear. This helps reduce engine wear that occurs during deceleration after a pass. We recommend this part for those of you running aluminum rods, as you'll get nearly double the life out of your rods. Our combination uses steel rods, and our shifter has no provision for an additional neutral so we'll stay with PN 121900.
Anytime you build a transmission for this kind of power and weight combination, there are several pieces that we consider mandatory. First is a bolt-in outer race for the overrunning clutch (also commonly referred to as the sprag). This piece is readily available from several manufacturers. We got ours from TCI. Next, you'll need to replace both the front and rear three-pinion planetary gearsets with four-pinion units. Rather than purchasing expensive aftermarket planetary gearsets, we set our sights on the salvage yards for these items. Chrysler actually put four-pinion planetary gears in many of their factory transmissions, so knowing where to look can save you a few bucks. The gearsets we're using came from a Winnebago motor home that utilized a '70 full-ton Dodge truck chassis. Finding the four-pinion planetary gears is somewhat hit or miss, but we've found that big-block truck transmissions from the late '60s through the late '70s are a good place to look.
The next item we consider almost mandatory is an aftermarket front clutch drum. The front drum takes the most abuse during first gear operation when torque multiplication is the greatest. If you've heard about or experienced a TorqueFlite grenading, it was likely caused by a front-drum failure. A factory steel front drum is adequate, but only if it has been checked for cracks by magnetic particle or dye penetrant inspection. Instead of taking chances with a factory front drum, we chose TCI's aluminum unit for two reasons. First, it is new and has already been inspected for defects that can cause failure, so we have peace of mind the drum will handle the abuse we'll give it. Second, the aluminum drum is lighter and frees up some ponies to send to the rear wheels, so we figure the TCI unit is money well spent.
Enough about theory, let's get on with the build so we can go racing. For our overhaul we enlisted the help of Tod Struck at Inline Performance Specialists in Bushnell, Florida. Tod has been a Chrysler specialist for more than 16 years and knows the TorqueFlite as well as anyone we know. He and his son are also avid drag racers and support several local Mopar racers with their transmission builds and chassis setups. We won't be covering the basics of transmission building in this article, rather highlighting the modifications required for a race transmission. For more detail on basic transmission building, refer to our "TorqueFlite Teardown" article in the November 2005 issue.