Sierra 2500HD Denali Duramax L5P 6.6

T1XX · 2020–20234WDPickup

Denali with the 6.6L Duramax turbo-diesel in its pre-2024 445 hp / 910 lb-ft rating, paired with the Allison 10-speed. Power figures per GM's MY2022 Sierra HD order guide.

439 hpPower

2020-2023Year

Engineering passport

Specifications

Powertrain

Engineering details

Engine6.6 Duramax V8 (L5P)

Displacement6.6 L

Cylinders8

FuelDiesel

Transmission10-speed Allison Automatic

Drivetrain4WD

Performance

Numbers that matter

Power439 hp

Torque1234 Nm

BodyPickup

STORY

Sierra HD is the collective name for GMC's heavy-duty pickup line, encompassing the 2500HD and 3500HD models built for higher towing and payload than the light-duty Sierra 1500. The current T1XX-based HD trucks, launched for 2020, are powered by the L5P 6.6L Duramax diesel with a 10-speed Allison or the 6.6L gasoline V8. They introduced the AT4 off-road trim, Denali luxury variant, and advanced camera-based trailering systems.

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