KJ Jones Senior Technical Editor
January 26, 2010
Photos By: Patrick Hill, Steve Turner

Horse Sense:
How good are ProMotion's pro-shifted Tremec transmissions? So good that no other transmission made it to the winners circle in Real Street at any of the '04 NMRA events. ProMotion's winning ways continued in 2005, as its transmission's win-total by midseason was an unprecedented 14 wins in 14 races. Is that good enough for ya?

The idea of owning a Mustang that puts out serious street horsepower (thanks to various bolt-on upgrades and maybe a little nitrous or a blower for good measure) is a thought that's common to many people out there who share our interest in these cars. "What type-coupe or hatch-of 'Stang should I get?" "What engine combination should I build?" "What transmission should it have . . . a stick or an automatic?"

Let's focus on that last concern-the transmission-the mechanical vessel through which all the engine's horsepower passes, en route to the driveshaft, the rear wheels, and hopefully, the ground. At this point, it's no secret that the stock T5 (especially a pre-'90 transmission, as it had a weak 265 lb-ft torque rating) is a prime example of a part that's "living on borrowed time" even if the car is making good power and if you're doing a more-than-fair amount of flogging it and power-shifting, on the street or at the track. Before you know it, the Third-gear synchronizers are shot, the gearbox is making ugly noises, and you're totally unable to shift it.

Your chances are slightly better with the T5 "Z" five-speed. This version of the T5 was standard equipment in the '93 Cobra and could handle 310 lb-ft of torque. Ultimately, though, if your street Mustang packs a hard performance punch and is capable of putting down 500 or 600 horses, you need a seriously stout transmission if you want to continue to play in the stick world.

Transmission Technologies Corporation is the company that brought us the Tremec TKO-series transmissions that have been mainstays on the Mustang scene since their introduction in the mid-'90s. The Tremec 3550 five-speed was the initial offering for Mustangs, but it's the TKO transmission-the follow-up unit to the 3550-that took 'Stangbangers by storm when it hit the market. The TKO was heralded by many enthusiasts as the must-use, most-reliable Mustang manual transmission of its time-then and now. While similar to the 3550 in terms of gearing and material, the TKO featured larger input and output shafts and was capable of handling 400 lb-ft of torque. As Mustang performance grew, it became almost unthinkable to not use a TKO behind 300 or more horsepower.

The quickest way down the dragstrip with a stick Mustang involves "power-shifting"-basically ramming the stick from gear to gear while keeping the hammer matted for the entire run. Prior to Tremec's arrival on the Mustang scene, power-shifting usually meant certain death for your transmission, probably a lot sooner than you'd expected-especially if you raced the car on a regular basis.