The T-45 and Tremec 3650 are both 5-speed manual transmissions used in Ford Mustangs during overlapping years, and they are easy to confuse. They are not interchangeable, so correct identification is important when ordering a replacement.
T-45: • Used in: 1996–2001 Mustang GT and Mustang Cobra • Output shaft: 28-spline • Bellhousing: Wider bolt pattern • Synchronized first gear (some early versions had issues with 1st gear synchronizer) • Known for relatively weak synchronizers under performance driving
TREMEC 3650: • Used in: 2001–2004 Mustang GT (note: 2001 was a transition year — some got T-45, some got 3650) • Output shaft: 31-spline (stronger) • Bellhousing: Updated bolt pattern • Upgraded synchronizer design compared to T-45 • Generally considered a stronger unit
EASIEST WAY TO TELL THEM APART:
1. Check the transmission ID tag: • The transmission tag is located on the driver's side of the case, usually near the shift tower or mid-case. • The part number or casting number on the tag will identify the unit. Look up the number against a Tremec/Ford parts reference.
2. Count the driveshaft splines: • Count the splines on the output shaft (where the driveshaft yoke connects). • 28 splines = T-45 • 31 splines = Tremec 3650
3. Input shaft diameter: • The input shaft diameter also differs between the two — the 3650 uses a slightly larger input shaft.
If you need help identifying your transmission before ordering, call us at 1-844-XPARTS-1 or email support@expediaparts.com.
