GMC Sierra 1999 - 2007 6.6 Duramax 365hp
Real standard and upgraded performance figures for the 6.6 Duramax 365hp engine in the GMC Sierra 1999 - 2007.
These are real standard and Stage 1 (and where available, Stage 2) figures for the GMC Sierra 1999 - 2007 6.6 Duramax 365hp — not a generic estimate for the model range.
| Horsepower (HP) | Torque (Nm) | |
|---|---|---|
| Standard | 365 | 894 |
| Stage 1 | 395 | 945 |
| Stage 2 | 410 | 970 |
- Make
- GMC
- Model
- Sierra
- Generation
- 1999 - 2007
- Engine
- 6.6 Duramax 365hp
- Fuel type
- diesel
Frequently asked questions
Is Stage 1 tuning safe for the GMC Sierra 1999 - 2007 6.6 Duramax 365hp?
Yes — Stage 1 for this engine is a software-only remap calibrated to stay within its stock mechanical limits (turbo, clutch, fueling), so no hardware changes are required.
How much more power does the 6.6 Duramax 365hp make after tuning?
Standard output is 365 HP / 894 Nm; Stage 1 on this engine typically reaches 395 HP / 945 Nm. Exact results can vary slightly with fuel quality and vehicle condition.
How long does a GMC Sierra 1999 - 2007 6.6 Duramax 365hp remap take?
Once your original file is uploaded through the member panel, most requests for this engine are completed within a few hours.
Can the 6.6 Duramax 365hp be reverted to its original file?
Yes — we keep the original file on record for the request, so the ECU can be put back to stock at any time.