In 1966, vehicle classification and rules were based on the SCCA's A and B Sedan amateur classes. A Sedan was called the Over 2.0-Liter category. The cars competing in the group were limited to a 5.0-liter engine and provided a platform to showcase the new 'Pony Cars.' The Under 2.0-Liter category included BMW, Alfa Romero, British Leyland and Porsche vehicles.

The Trans Am series and its regulations have evolved over time. The championship has changed the race formats, vehicle eligibility and rules governing the cars.

Currently, the races are 100-miles in length with no opportunity for a pit stop to change drivers or tires and refuel the car. Teams can also compete in two championships – Trans Am Championship and Trans Am West Coast Championship.

Trans Am Championship

• February 22-25 - Sebring International Raceway
• March 21-24 – Road Atlanta
• April 11-14 – NOLA
• May 10-11 – World Wide Technology Raceway
• May 24-27 – Lime Rock Park
• June 7-9 - Pittsburgh International Race Complex
• June 20-23 - Mid-Ohio Sports Car Course
• June 27-30 – Road America
• July 19-20 – Lime Rock Park
• August 21-25 – Watkins Glen International
• August 29 - September 1 – Canadian Tire Motorsport Park
• October 3-6 – VIRginia International Raceway
• October 31 - November 3 – Circuit of the Americas

Trans Am West Coast Championship

• March 1-3 – Thunderhill Raceway
• April 18-21 – Sonoma Raceway
• May 2-5 – WeatherTech Raceway Laguna Seca
• July 26-28 – Portland International Raceway
• October 18-20 – Spring Mountain Motorsports Ranch
• October 31 - November 3 – Circuit of the Americas

In 2024, there are five classes – Trans Am, Trans Am 2, Xtreme Grand Touring, Super Grand Touring and Grand Touring. Trans Am, Xtreme Grand Touring, Super Grand Touring and Grand Touring compete in the same event. Tran Am 2 drivers have their own race.

• Trans Am (TA) – This is the series' quickest class. These tube-frame race cars are powered by a naturally aspirated 366-cu.in. pushrod V8 engine, which produces over 850-horsepower. From a technological standpoint, the vehicles are kept relatively simple – no superchargers, turbochargers, anti-lock braking systems or traction control. The body styles used are the Ford Mustang, Chevrolet Camaro, Cadillac CTS-V, Chevrolet Corvette and Dodge Challenger.
• Trans Am 2 (TA2) – These are also tube-frame chassis cars. Unlike the TA category, these vehicles use electronic fuel injection and intake restrictor plates to limit the horsepower to approximately 490. To keep expenses down, the series officials set the maximum price for shock absorbers, wheels, brake pads, and calipers. For example, shock absorbers are limited to $850 each. This category is also restricted to using a four-speed manual transmission with no overdrive. Teams are also prohibited from using superchargers, turbochargers, anti-lock braking systems or traction control. The most common body style is the Chevrolet Camaro, but the Ford Mustang and Dodge Challenger are also eligible.
• Xtreme Grand Touring (XGT) – This class was created to give former FIA GT3 cars a place to race. The category is open to a wide range of GT3 vehicles - Audi R8 LMS, Porsche 991.2 GT3 Cup, Mercedes AMG GT3 and Chevrolet Corvette.
• Super Grand Touring (SGT) – In 2019, TA3 was renamed SGT and included many production-based vehicles. Unlike TA and TA2, which are restricted to North American models, European manufacturers may compete in this division. As a result, the list of vehicles eligible for SGT is long and ranges from the BMW M3 to the Dodge Viper. Some cars are fitted with restrictor plates or carry additional weight to maintain parity.
• Grand Touring (GT) – The Grand Touring was previously called TA4. A wide range of European and American vehicles are also eligible to compete in this group – the list is not as lengthy as the Super Grand Touring category. This is viewed as an entry-level category that only allows limited preparation. To equalize performance, some cars may carry additional weight or the engine may be fitted with a restrictor place.

• Trans Am launched the Trans Am Pro/Am Challenge in 2021 as a new crossover program to introduce SCCA drivers to Trans Am. The Trans Am Pro/Am Cup Challenge allows SCCA drivers to compete in Trans Am using the same basic SCCA road racing trim for their cars, making the transition back and forth between the SCCA Road Racing program and Trans Am seamless.

Round nine of the 2024 CUBE 3 Architecture TA2 Series was held at Watkins Glen International. Drivers completed in a thirty-lap contest around the eleven-turn 3.337-mile road course.