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New Doorslammer Differentials: Engineered to Handle The Horsepower
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Todd Silvey February 04, 2020Pro Modifieds, along with a bevy of extreme doorslammer class racers, are continuously developing more power to put to the pavement. Those power levels come with a price: increased strain on drivetrain hardware. Each individual component between the crankshaft and the dragstrip now faces the scrutiny of re-engineering.
Racers and chassis builders have made recent strides to improve upon the competition differential. The days are counting down for a well-built 9-inch Ford rearend to continue to have the ability to handle today’s load dynamics.
Insert the now typical 3,200- to 3,500-horsepower in front of a standard 9-inch gear design, and you are effectively welding the differential gears together under the extreme tooth pressures during a 5-second dragstrip pass. Many manufacturers have developed various ring gears ranging from 9.5- to 11-inches in diameter — these larger gears offer additional strength to handle the extreme loads.
To house these beefiest of 10.5- and 11-inch gear sets has required a fresh approach to the entire differential housing. It’s nothing new for nitro and alcohol racers to utilize various “clean slate” engineered rearend housings of modular design. These designs are now also being applied to the doorslammer. In many cases, these door cars are rivaling the power that nitro and alcohol classes produced in the 1980s and early ’90s.
Justin Carmack has developed his own offering in the new realm of extreme horsepower differentials with his unit combining his Carmack Engineering manufactured components with Mark Williams Enterprises hardware.