The new offerings from Mopar are a breath of fresh air for those of us unable to purchase a rear-wheel-drive V-8-powered automobile from Chrysler Corporation until recently. And while you may or may not like the fuel injection and electronics on your new Mopar, you must admit doing a burnout with a Hemi under the hood and smoke coming from the rear tires is how it was meant to be. The amenities of late-model Mopars are also easy to get used to, as is the reliability of driving a newer automobile. We couldn’t wait to get ours, which meant opting for the automatic transmission version since those were the first ’09 R/Ts produced. We’ve really enjoyed driving our Challenger, and while the Chrysler NAG1 five-speed automatic transmission has worked perfectly so far, we know we’re pushing our limits since our engine is modified with a Procharger intercooled supercharger kit.

Since owning our Challenger R/T, we’ve lowered the car with an Eibach sport suspension kit, adding larger diameter sway bars as well to improve the handling characteristics, and also installed Magnaflow exhaust. We’ll be addressing other areas of our vehicle, such as lightening it up, improving the brakes, upgrading the wheels and tires, and increasing the fuel system’s volume in future articles as we prepare for the ultimate goal of replacing the factory engine with a larger displacement version containing forged internals. This month we’ll continue our modifications, upgrading our car’s automatic transmission with a high-performance replacement NAG1 from Gearstar Performance Transmissions.

The professionals at Gearstar Performance Transmissions are known for the quality of their engineered transmission and torque converter assemblies, can provide a transmission to fit any of your needs, from mild to wild, and even have a NAG1 unit in a Jeep SRT8 that is rumored to run the quarter-mile in the 8s. They build TorqueFlite transmissions as well, delivering any level of performance desired, and each transmission is assembled by a dedicated builder, then dyno tested when complete. Since the NAG1 transmission in our Challenger will be used not so much for racing but in a moderately powered street car, Gearstar prepped ours to easily handle the power our combination will make, and has NAG1 units available to handle up to 1,100 lb-ft of torque and 1,100 horsepower. As part of the package, they also sent a well matched converter for our combination, with much improved lockup clutch capacity. And if we need a beefier transmission in the future, we can just send our unit back to Gearstar for the latest upgrades.

Before simply swapping the transmission, let’s discuss Mopar’s new automatic, what led to it, and how it works. When the LX cars were debuted in 2005, Daimler still owned a big chunk of Chrysler Corporation, and the companies obviously shared technology freely. Throughout the Charger, Magnum, 300, and Challenger, you can see the Mercedes engineering in the suspension and brakes, and even in areas like the door seals. This thoroughbred influence was good for Chrysler, resulting in well-engineered cars that are fun to drive and technologically sophisticated, with computers controlling nearly every aspect of the vehicle, including the transmission. Designated by Chrysler as the NAG1 five-speed automatic, the unit is actually a Mercedes part number 722.6 transmission that dates back to 1996.

Used primarily in passenger cars, the Mercedes 722.6 (NAG1) is a hydraulic automatic transmission with many similarities to older designs but many differences as well. Instead of using hydraulic pressure, valves, and a governor to control up and downshifts, the NAG1’s valvebody contains a series of computer actuated relays to control these functions. Additionally, the converter is a lockup model, again with a computer controlling when the converter locks up partially, or completely. As you’re noticing, this is a sophisticated unit, using planetary gear sets, multiple clutch packs, and even internal brakes, which is why we didn’t take the chance of upgrading it ourselves.