Engines and modifications Sierra 2500HD V (GMTT1XX, facelift 2024) Regular Cab Long Bed

6.6 V8 (401 Hp) Automatic

6.6 V8 (401 Hp) 4WD Automatic

6.6 Duramax TD V8 (470 Hp) Automatic

6.6 Duramax TD V8 (470 Hp) 4WD Automatic