All major manufacturers have at least one transmission that serves as the backbone for their automatic shifting needs in the world of performance/street and racing, and for the majority of Chrysler products it's the venerable A727. Beginning in 1962 when it replaced the heavy cast-iron–cased A488, the 60-pound lighter aluminum-cased 727 came with numerous improvements, including an inch-larger 11.75-inch torque converter and beefed-up internals. Known as the TorqueFlite, when it comes to varied service use and abuse, it's hard to beat this guy. The new workhorse trans had to be able to handle just about anything the Pentastar people needed. Think about it: TorqueFlites (in 727 and lighter 904 form) have been installed behind everything from Slant Sixes to Super Stock Hemis. These things have hauled groceries, heavy loads, and ass down the dragstrip. They've been neutral dropped, Mannix turned, and subject to all manner of hard use in Chryco muscle cars.

And they were good at it too; Chrysler installed them in various cars and trucks up until the 1980s. When the need for an overdrive-enabled trans arose, the A727 morphed into the A518 (46RH/46RE), and then the A618 (47RH/47RE). They had fancier names, another gear, and modern electronics, but they're all basically A727 architecture. Those transmissions were installed in various rear-wheel-drive platforms up until 2007. The 48RE that was used behind Cummins diesels and V-10s in 2500- and 3500-series trucks is also of 727 ancestry. Though it faded from use for a while, the TorqueFlite name is so associated with strength that Chrysler even revived it recently.

When we decided to work with Indy Cylinder Head to build the 657hp aluminum monster for our 1968 Valiant project, we knew it would be the deciding factor for the rest of the driveline. Everything had to be up to the task repeatedly and reliably. For the trans, the A727 was the logical choice, and TCI's StreetFighter version fit our needs perfectly. Built to withstand the toughest street machines, the StreetFighter has upgraded clutches and bands, new sprags/roller clutches to increase holding capacity, an improved lubrication system that increases fluid flow to planetaries and internals, and higher line pressure for extra firm shifts and greater torque capacity with less slippage. We're planning to put all of that stuff to the test. Check out how this critical link for our Valiant came together at TCI's headquarters.

We show you how TCI built an A727 TorqueFlite StreetFighter to handle the 657hp punch from our Indy low-deck big-block.