Duramax 6.6L LML V8
Horsepower
397 hp
Torque
765 lb-ft
Years produced
2011–2016
Aspiration
Turbocharged
- Configuration
- V8, 6.6 L
- Aspiration
- Turbocharged
- Builder
- DMAX Ltd.
- Designers
- Joint venture of GM and Isuzu (DMAX); engine blocks supplied by Fritz Winter
- Years
- 2011–2016
Offered in: Chevrolet Chevrolet Silverado 2500HD, Chevrolet Chevrolet Silverado 3500, GMC GMC Sierra 2500HD, GMC GMC Sierra 3500
The LML brought a Bosch CP4 high-pressure pump rated for up to 20 percent biodiesel and a urea (DEF) injection system to the Duramax for 2011. Output was 397 hp and 765 lb-ft, paired with the six-speed Allison automatic. It ran through the end of the GMT900 generation and into the 2015 and 2016 models before the L5P replaced it.
What made it successful
It raised power and torque substantially while meeting the newer emissions rules through a DEF system.
Market position
Its 765 lb-ft was a large jump over the LMM's 660. Sourced comparisons with Ford and Ram are not yet included.
Rebuild Potential
Tier CEditorial opinion.
The LML has full parts and community support, but every engine uses the CP4 pump, whose catastrophic failure is the dominant risk and a major repair bill. Added DEF and EGR complexity compounds that. It is a candidate only where the buyer accepts the fuel-system risk. Any change to the fuel system should be checked against emissions rules.
Best year ranges
- 2011-2016: No year stands out; every LML uses the CP4 fuel pump.
Known weak points
The Bosch CP4.2 fuel pump can fail catastrophically, sending metal debris through the entire fuel system at repair costs reported around $8,000-12,000.
Common fix: Replace the pump and the whole contaminated fuel system with OEM-spec parts, and keep fuel filtration current.
The added DEF injection and emissions plumbing create more potential failure points, including the EGR cooler.
Common fix: Service or replace failing emissions components with compliant parts.
Common upgrade categories
- OEM-spec fuel pump and filtration
- Fuel supply monitoring
- EGR cooler and DEF component service
- Transmission and cooling upgrades
This engine is emissions-equipped (EGR, particulate filter and, from 2011 on some engines, DEF/SCR). Keep the emissions equipment the truck was built with; repair or replace it with compliant parts. Removing or defeating it on a vehicle originally equipped with it is illegal under federal law. Rules vary by state (for example California/CARB), so check local law and model-year requirements before modifying.
Sources
- Duramax V8 engine (Wikipedia) (accessed 2026-09-18)
- Chevrolet Silverado HD (Wikipedia) (accessed 2026-09-18)