The 2003 Mustang lineup offered multiple transmissions depending on model: most non-Cobra Mustangs could be equipped with a 5-speed manual Tremec T5 or a 4-speed automatic (4R70W), while the SVT Cobra used a 6-speed manual Tremec T56.
Non-Cobra Mustangs: V6 and GT
The base and GT models offered two primary options: a traditional five-speed manual and a four-speed automatic, both commonly found across these trims.
- Five-speed manual Tremec T5 (V6 and GT)
- Four-speed automatic 4R70W (V6 and GT)
These options gave buyers flexibility between performance and convenience, with the manual favored by enthusiasts and the automatic preferred for everyday driving.
SVT Cobra (2003–2004)
The high-performance Cobra line used a dedicated drivetrain: a six-speed manual Tremec T56, optimized for the supercharged 4.6L V8. There was no automatic option.
- Six-speed manual Tremec T56 (Cobra)
For 2003-2004 Cobras, the six-speed manual remained the sole transmission configuration, matching the car's intent as a track-focused performance model.
Summary
In short, the 2003 Mustang offered two broad paths: V6/GT models could be ordered with either a 5-speed manual (T5) or a 4-speed automatic (4R70W); the Cobra was equipped exclusively with a 6-speed manual (T56).