American Powertrain Now Offers Turnkey ProFit™ 5- and 6-Speed Transmission Conversion Kits for GM 1977 – ’90 B-Bodies

Perfect Fit, Optimal Driving Performance, Improved Fuel Economy

Cookeville, TN (August 11, 2026) – American Powertrain, a leading source for modern overdrive systems, now offers its popular 5- and 6-speed ProFit™ TREMEC^® transmission conversion kits for GM B-body vehicles built between 1977-1990. This ProFit kit is especially engineered for “boxy” or square B-body platform vehicles popular at the height of the full-size car craze, including Caprice, Impala, Coupe DeVille, Bonneville, Delta 88, LaSabre, and Estate wagons. 

Designed as a single-box solution that takes the trouble out of sourcing components for a manual conversion, the ProFit kit offers owners of these popular full-size vehicles the joy of experiencing smooth, trouble-free shifting, improved fuel economy, and a more fun cruising experience. 

The 5-speed kit includes a TREMEC TKX 5-speed transmission has 8,000 rpm shift capability and 600 ft/lbs of torque capacity. Components include the correct shift location AP Revolution or White Lightning shifter and shifter knob, driveshaft slip yoke, bolt-in B-body steel crossmember, polyurethane transmission mount, pilot bearing, and proper wiring harness. 

The 6-speed ProFit kit is sold with TREMEC’s dual-overdrive, high-performance Magnum 6-speed transmission, which handles up to 700 lb-ft of continuous torque. Included in this kit is an AP Revolution or White Lightning shifter mechanism, driveshaft slip yoke, bolt in B-body steel crossmember, polyurethane transmission mount, tunnel patch, pilot bearing, and proper wiring harness. 

Other optional parts include a new bolt in hydraulic clutch pedal which was never an option on these cars, bell housing, flywheel, shifter and shifter handle upgrades, twin disk clutch, and more. 

American Powertrain Marketing and Sales Manager, Matt Graves, says, “Obviously I’m a fan as we used my 1983 Cadillac Coupe DeVille, the ‘Chicken Coupe’ as our R&D platform for these kits. This took time to develop, but we wanted to make sure that when we launched, we had the right configuration that could be tailored for fit and performance options. I feel confident we are going to see a lot more B-body manuals next year. Fuel costs are through the roof, and this conversion can save you on fuel alone, not to mention it is just more fun to drive a stick. The big piece of the puzzle was the UnderDash Hydraulic clutch pedal. That was a game changer to have a bolt-in clutch pedal for this platform that never came with a clutch pedal.” 

All ProFit kits are made in the USA, covered by American Powertrain’s two-year warranty, and can still be purchased with 0% financing for up to six months. For more information about the ProFit 5- or 6-speed transmission conversion kits for GM B-bodies, visit here.

For more information about a ProFit 5- or 6-speed modification for GM B-bodies (1977-1990), view this video or visit American Powertrain, the world’s largest TREMEC distributor, at AmericanPowertrain.com.  To speak now with one of American Powertrain’s highly qualified sales technicians, call 931-646-4836.