Classes
Heavy Super Stock Diesel Tractors - You might call the Super Stock an unlimited version of the farm appearing tractor classes. Although they may appear on the outside, but produce many times over their factory rated horsepower. As the name implies, diesel is the only fuel allowed in the Super Stock Diesel division. These IH, Agco, and John Deere machines produce around 2,500 to 3,000 horsepower with their stock engine having up to four turbo chargers flowing the air mixture.
Modified
Tractors - Modified Tractors can use virtually any number and
type of engines and compete at a maximum weight of 7,500 pounds.You will see competitors in this division run 3 to 4 super charged
V-8's, 2 allison aircraft engines, or 3 turbine engines. These
engine combinations will produce between 6,000 to 8,000 horsepower,
making it one of the most powerful motorsports in the world. You
will actually feel the power when you watch them live!
Super Semis - Tractor Pulling is called the Heaviest Motorsport on Earth and the Super Semis are the heavyweights of tractor pulling. Weighing in at 20,000 lbs., these behemoths overshadow everything else on the pulling track and for that matter, anything else in motorsports. When they come thundering down the track, the heavier the load gets, the harder they pull. Sometimes you wonder if they'll ever stop. The Super Semis are one of the most popular divisions of NTPA pulling.
Pro Stock Tractors -
The "Pro Stock" division gets us a little closer to those tractors you see in the fields. This division by rule must maintain many of its "stock" components such as engine block, transmission housing, and final drive housing. Engine size is limited to 680 cubic inches, but injector pump and allowed, single turbocharger can be of any size. These tractors compete at 10,000 lbs., the heaviest of the tractor classes.
Mini Modified Tractors -
The "Minis" are the undisputed kings in the motorsport world when it comes to "power to weight" ratio. An amazing one horsepower per pound combined with a wheelbase of less than 100" also qualifies the "Minis" as the "wildest ride on four wheels", although they aren't using all four most of the time. At 2,000 lbs., the Minis are the lightest division in NTPA competition and are probably the toughest to drive. Keeping the tractor in a straight line heading down the track is the biggest challenge a driver in this division faces.