With the S197 Ford Mustang celebrating 20 years, we thought we’d share some TREMEC-related history related to the car. The S197 was one of the most significant redesigns in Mustang history, drawing heavily on retro styling cues when it debuted for the 2005 model year. After 25 years on the Fox Body platform, the S197 introduced a completely new architecture. The TREMEC TR-3650 5-speed manual transmission continued its role that started in the 2001 Mustang, delivering strong performance and capability in this next-generation Mustang.
ABOVE: The S197 Mustang debuted for the 2005 model year and took the retro style car design trend to a whole new level. It hearkened back to the 1967-1968 Mustangs that were a big part of the muscle car era. The Mustang GT had 300 horsepower from the factory for the first time since the 1970s and, when paired with the TREMEC TR-3650 5-speed manual transmission, was one of the best-performing Mustang GTs of all time.
For base models, the long-running 3.8L V6 was replaced by a 4.0L SOHC V6 with additional power and torque. The Mustang GT moved from the 4.6L two-valve SOHC V8 to a new three-valve version that improved airflow and increased output. The change delivered 300 horsepower and 320 lb-ft of torque — a 40-horsepower jump over the 2004 GT 4.6L SOHC V8.
With the gearing of the TREMEC TR-3650, the 2005 Mustang GT in stock trim recorded quarter-mile runs of 13.8 seconds at 102 mph. The 0-60 mph time was 5.2 seconds, and the new front and rear suspension made the S197 one of the best-handling factory Mustangs to date, despite weighing about 500 pounds more than its predecessor. The TR-3650 gearing and Overdrive also made highway cruising efficient, allowing the GT to achieve 23 to 24 mpg while running 75 to 80 mph (something we recently verified driving a 2005 model on the Route 66 to The SEMA Show 2025 event that TREMEC sponsored.
ABOVE: The TREMEC TR-3650 5-speed was developed as a replacement for the TREMEC TR-45 that had been the Ford Mustang GT and Cobra manual transmission option from 1996 through 2001. It replaced the TR-45 midway through the 2001 model Mustang production. It was designed to handle a larger diameter clutch (11-inch versus 10.5-inch) and featured a new synchronizer design for increased strength and shift quality.
The TREMEC TR-3650 was first introduced midway through the 2001 model year as the replacement for the TREMEC T-45 5-speed. It was engineered to support a larger 11-inch clutch (versus the previous 10.5-inch unit) and featured an updated synchronizer design for improved strength and shift quality. Additional upgrades included built-in positive non-adjustable shift stops and carbon-fiber synchronizers. Gear ratios remained close to the T-45, but for the S197 Mustang GT the TR-3650 received a slightly lower First gear (3.38:1 versus 3.37:1) and a lower Reverse gear (3.77:1 versus 3.32:1). It was also updated to work with a hydraulic clutch slave cylinder and throw-out bearing assembly, replacing the previous cable-actuated system.
If you’re in the market for S197 to build into a hot rod or race vehicle, know that the manual transmission they came with will deliver great performance in stock form. And the TREMEC Magnum XL 6-speed is a great upgrade to add significantly higher torque-input capacity and eliminate the factory remote shifter setup.