Swapping out the factory rear end gears and differential of your Mustang is one of the best ways to change the entire character of your 2005 to 2009 Mustang GT. Many Mustangs came from Ford with either 3.31 or 3.55 gears (a few did come with 3.73s) that were thrown in to skew fuel economy slightly higher in the MPG ranges than give you outstanding performance. Grabbing a set of 3.73, 4.10, or even more aggressive gears from Motive Gears or Ford Racing will really make your Pony come alive and hop off the line like a true race car. Our most popular gears are 3.73s which provide a nice change of pace for your Pony without the need to constantly shift. 4.10s are a great choice for the Mustang that sees a good bit of track time. We even have a selection of limited slip differentials and performance differential covers that can help improve your Mustang's handling and increase the lifespan of your rear end. Once you have a few rear end upgrades picked out, take a look at our clutches and flywheels, or engine performance parts.