Serpentine Performance Ratio Pulley Set

The Steeda Underdrive Pulleys (555-3305) are a performance-enhancing upgrade designed for various Ford Mustang models. These serpentine-style pulleys are manufactured with a performance ratio to reduce parasitic power loss by slowing down the accessories driven by the serpentine belt. The result is a slight increase in horsepower and potential for longer accessory life. Installation of these underdrive pulleys has been documented for 2001-2004 Mustang GTs with the 4.6L 2V engine, as well as 2005-2010 Mustang GT models. Some users have reported positive experiences, noting that they free up a few horsepower and contribute to better accessory performance. While generally well-received, some forum discussions have touched upon potential concerns, including discussions about oil pump failures in relation to underdrive pulley installations. However, other users have reported no such issues.