While standard magazine protocol involves pulling the handle on the dyno, patting yourself on the back, and calling it a day, readers want more than just engine buildups destined to languish idly as pricey garage decorations. To make amends for these pathetic wastes of horsepower, back in the June issue we chronicled the build of a 532ci big-block Ford that spit out 775 hp and 673 lb-ft on pump gas. This big lump was conceived with an actual purpose in mind-go figure-and that's to drop it on a full-weight '93 Mustang notchback, run solid 9s on drag radials and a stock-style suspension, and survive the 200-mile roundtrip trek to the dragstrip while maintaining street legality. With the key ingredient in the powertrain complete, the next step is selecting a trans capable of surviving the harsh demands of a dual-purpose street/strip role. Given our needs, it only makes sense to go hybrid.
Although our decision to run a GM TH400 will surely bunch up some Blue Oval panties, it's been the benchmark heavy-duty drag automatic for decades. Not only have countless Ford and Mopar buffs put brand loyalty aside and bolted them into their project cars, but the TH400's legendary reputation for durability has infiltrated the hallowed turf of Euro elitists as well. Despite their superior technical aptitude-at least that's what they try to tell us-prestigious marques such as Ferrari, Rolls-Royce, Bentley, and Jaguar have all used TH400s in their past rides. Likewise, U.S. troops abroad rely on trusty TH400-equipped Humvees while evading the bad guys' bullets and IEDs. Granted, a Ford C6 can be built to handle our intended application, we opted for the TH400 due to its lower mass, superior efficiency, smaller dimensions, and more readily available parts. Furthermore, adapting a Turbo 400 to fit behind a Ford mill is very straightforward
Thoroughly impressed with the fine work he performed on Project Talladega's 700-R4, we once again turned to Greg Ducato of Phoenix Transmissions. He set us up with one of his company's PT400SX-model Turbo 400s, which can easily handle 900 hp. To improve upon what's already a rugged trans from the factory, Phoenix's bag of tricks include high-capacity clutch packs, a 300M billet steel input shaft, a five-pinion rear planetary, a billet clutch hub, a Kevlar band, and a 34-element sprag. This is surely one stout piece, but in the walk of performance transmission rebuilds, it required very little work to elevate the TH400's durability to such impressive levels. "If you want a gnarly brute of a no-compromise transmission and need dead nuts reliability, you need to go with a Turbo 400. You can take a lighter-duty trans like the TH350 and bring it up to the same level as a TH400, but that requires a ton of trick parts," Greg explains. "At the end of the day, you'll have a TH350 that costs more than a TH400 that's still an inherently weaker design. The only downside to a Turbo 400 is that its rotating mass is greater-which equates to more parasitic loss-but if you're making huge power to begin with, it's a small price to pay for the added durability. The few hundredths of a second you might pick up at the track with a TH350 may be important if you're racing in an extremely competitive class, but the average guy on the street will never feel the difference." Since it was quite obvious who the real expert was, we let Greg do all the dirty work, and documented the intricacies of building a bulletproof Turbo 400.
With a PML deep cast pan,...
With a PML deep cast pan, slick case finish, and beefy J.W. bellhousing, the Phoenix PT400SX TH400 certainly looks the part of a beastly automatic. Rated at 900 hp, its $1,645 list price-which includes a custom converter and a two-year, 24,000-mile warranty-is a raging bargain.
There are several methods...
There are several methods of adapting a GM TH400 to a big-block Ford, but the most practical for a track-oriented application is with an Ultrabell bellhousing from J.W. Performance Transmissions. It features the Ford bellhousing bolt pattern on one side, and attaches to the TH400's front cover on the other side. Of course, this requires cutting off the factory bellhousing using a template included in the J.W. kit. With the measurements scribed on the case, the old bellhousing was hacked off with a plasma cutter. Afterward, final shaping was performed using a hand file to ensure a close fit to the trans case.