With the case removed you can see the guts of the transmission. Five speeds, three planetary gearsets.

The Chrysler NAG1 five speed overdrive transmission.

Late Model NAG1 Transmission Upgrade

Back when Chrysler was owned by Daimler-Benz a new platform of cars was developed for the Chrysler brands, the LX. This platform underpins the Gen I Chrysler 300, Dodge Charger and Magnum and with a few dimension changes the Dodge Challenger. The first generation cars have a lot of parts from the Mercedes parts bin—suspension, rear ends, and what we’re interested in here, the transmissions.

Our late model project car, the Maulin’ Magnum a 2007 Dodge Magnum SRT8, sees far more abuse then any street car and almost all street/strip cars for that matter. The car has over 50,000 miles on it and nearly 500 quarter mile passes, most with nitrous oxide or a supercharger. The car has a tow hitch and pulls a nearly 2,000 pound trailer with gear to races all over the southwest. Then we unhitch, swap wheels and tires, strip out some weight and go racing.

And the car is a good race car; with Alex Rogeo at the wheel the car has made four final rounds and this year earned runner up in the PSCA Street Muscle championship, going seven rounds in the final race. We continue to be impressed by this wonderful platform and the versatility of this Mopar machine.

That said, we begin to notice some shifting anomalies in the early summer which showed up clearly in the data logs. Something wasn’t right in transmissionville. Now again, remember that this car makes about 660 horsepower and has 50K miles on it, 500 quarter mile passes with WOT shifting and hard launches, towing up desert highway grades in 113 degree temperatures, well, you get the point—our 50,000 miles are probably more like 150,000 or more of normal use.