1993 Big Block Ford Mustang - Hybrid Drive

After cutting off the stock bellhousing, the TH400 case is cleaned and prepped in a proprietary process that not only yields a brilliant finish, but also closes up porosity for added strength. The seven-step procedure involves bead blasting, steam cleaning, flat filing, casting flash removal, and a bath in a tub full of vibrating ceramic alloy media and brightening solution.

High-quality OE-style frictions (brown) work great for most buildups, but for extreme-duty applications, such as in our project Mustang, Phoenix prefers using semi-metallic, waffle-pattern (gray) clutches. The extra grooving in the clutch face helps displace fluid when the clutches apply, which promotes positive engagement and heat dissipation.

For no-compromise durability, Phoenix's TH400 utilizes a straight-cut sun gear, and front and rear planetaries. While the ratios remain unchanged from stock, the straight-cut gears substantially reduce thrust loads at the expense of gear whine. The added noise is most noticeable in lower gears, but it's a small price to pay in a heavy-duty drag application.

The long shelf life of the TH400 means that it can benefit from revisions made to its successors. For instance, this five-pinion rear planetary assembly out of a 4L85E is substantially stronger than the TH400's four-pinion unit, as it distributes torque over a greater surface area. Note the straight-cut gears.

Whether you're building a motor or a trans, it's the little things that distinguish the studs from the duds. The later-style Torrington bearing set (top) features a greater number of rollers than its stock counterparts, which beefs up load capacity.

The low-reverse band is subject to tremendous loads under heavy throttle, as it holds the heavy reaction carrier in manual-low and reverse. Likewise, increased line pressures exert additional stress on the band as it engages. Compared to the stock band (left), the aftermarket unit (right) has wider contact points for the lugs, and carbon-blended lining material.

Heavy-duty low-reverse sprags (bottom) are equipped with larger springs and a reinforced cage design. This provides a more stable contact area for the sprag rollers, which must support the loads exerted on them by the reaction carrier assembly.

The stock stamped steel intermediate apply piston (right) is prone to deflection in high-hp applications. Not only is the cast aftermarket piston stronger, it features additional clutch contact area for increased holding capacity.

It doesn't look like much, but aftermarket Teflon rings (bottom) are preferred over factory cast iron rings in high-performance TH400 builds. At high rpm, iron rings will stick, bind, and wear into the clutch drums. Teflon rings offer far better sealing ability under high rpm and increased line pressure. Furthermore, the stock plastic thrust washers were replaced with steel and bronze units for enhanced durability.