FTI Performance TH400 Level 4 Transmissions TH400-4K21

Of FTI's three TH400 Level 4 builds in this group, the TH400-4K21 is the complete kit: it is the only one of the three bundled with its own billet torque converter, rated to a 3,400-3,800 rpm stall, plus a full cooler system already attached.

What is built into the case

Thirty splines turn a hardened-steel input shaft built in the TH350/400 style, paired with a billet steel clutch hub and a 2.43 first gear; the black-finished OEM-style case holds a deep aluminum pan. A trans-brake sits built into the full manual valve body for launch control, while heavy-duty steels and clutches, an intermediate sprag rated at 34 elements, a high-flow pump, race prep on the case itself, and a billet forward clutch hub all add strength; the unit carries an SFI 4.1/30.1 rating.

What is included to get it running

Because this is the kit version, performance ATF, a locking dipstick, and the cooler system ship with it, along with 12 quarts of fluid, so most of what is needed to fill and run the transmission arrives in the box; a wiring harness is left out.

Q: Does this come as a remanufactured unit or new? It is listed as remanufactured, rebuilt around FTI's Level 4 upgrades rather than assembled new.

Q: What kind of builds call for this one? Rated at 900 advertised horsepower, FTI aims this complete kit at drag cars and other high-powered vehicles that need a trans-brake-equipped automatic ready to install.