Redesigned Grand Prix arrives with GT models using the 200-hp naturally aspirated 3.8L and GTP using the new 260-hp supercharged 3.8L Series III. The optional Competition Group adds TAPshift, performance tuning and chassis/electronic upgrades.
Platforms / GM W-Body / W3 / Pontiac Grand Prix
2004–2008 · W3
Pontiac Grand Prix
The final Grand Prix generation combined three distinct enthusiast personalities: a 200-hp naturally aspirated 3800, a 260-hp supercharged Series III 3800, and the 303-hp LS4 V8 GXP. It is the most performance-dense model family in the W3 chapter.
Model years2004–2008
Body4-door sedan
Enthusiast trimsGTP · GT S/C · GXP
Top engineLS4 5.3 V8
Top output303 hp
MODEL-YEAR CHRONOLOGY
How the enthusiast story developed
Trim names simplify and the GXP arrives during the model year with the 303-hp LS4 V8. The GXP becomes the new top-performance model.
The GTP badge is dropped; GT now identifies the 260-hp supercharged model. Base, GT and GXP form the performance ladder.
The same basic hierarchy continues: 200-hp base, 260-hp supercharged GT and 303-hp GXP.
The supercharged GT is dropped. Base and GXP remain for the final year of Grand Prix production.
POWERTRAIN GUIDE
Engines that matter to enthusiasts
| Trim / era | Engine | Factory output | Enthusiast role | Transmission family |
|---|---|---|---|---|
| Base / GT (early) | 3.8L L26 3800 Series III | 200 hp / 230 lb-ft | Durable N/A platform context | 4T65-E |
| GTP / GT S/C | 3.8L L32 supercharged 3800 Series III | 260 hp / 280 lb-ft | Primary V6 performance platform | 4T65-E HD |
| GXP | 5.3L LS4 V8 | 303 hp / 323 lb-ft | Factory halo; V8 FWD chassis package | 4T65-E HD |
OWNERSHIP & BUILD FOCUS
What matters now
Supercharged identity
The 2004–2005 GTP and 2006–2007 GT carry the L32 supercharged Series III 3800. The badge changed; the enthusiast mission did not.
GXP is more than an engine
The GXP adds chassis, brake, steering and electronic changes around the LS4. Treat it as a complete package rather than a base car with two extra cylinders.
Age matters now
Transmission condition, cooling-system health, suspension wear, hub bearings and electrical issues deserve the same attention as engine output on any surviving car.
Open GTP / GT Supercharged deep dive → Open Grand Prix GXP deep dive →
REFERENCE STANDARD
Master Customs prioritizes factory-era documentation and period road tests, then uses established enthusiast references for service and ownership context. Equipment changed by model year and RPO; verify a specific car by VIN/RPO and factory service information before ordering parts.