The 6.6-liter LMM Duramax V8 diesel engine was introduced midway through the 2007 model year, when it replaced the 6.6 liter LBZ Duramax variant. As such, it powered Chevrolet Silverado Heavy-Duty and GMC Sierra Heavy-Duty pickup trucks through 2010. During that time, the LMM had an SAE-certified rating of 365 horsepower and 660 pound-feet of torque.
Notably, GM was able to improve the Duramax V8’s performance despite more restrictive emissions regulations. Another accomplishment during this time period is the fact that the millionth Duramax V8 engine built was an LMM, assembled in April 2007.
| Displacement: | 6.6L / 403 cu. in. |
|---|---|
| Aspiration: | Natural |
| Vehicles: | Chevrolet Silverado HD, GMC Sierra HD |
| Introduced: | 2007 model year |
| Discontinued: | 2010 model year |
| Predecessor: | LBZ Duramax V8 |
| Successor: | LGH Duramax V8 |
| Assembly: | Moraine, Ohio, USA |
The LMM’s release was a response to tightening emissions controls, though that didn’t prevent GM from devising innovative ways to refine the power plant. For instance, the engineers added an intake airflow valve, which regulates Exhaust Gas Temperatures (EGTs). GM also implemented a revised head design featured more efficient and effective coolant passages.
The ability to dissipate heat is already a critical component in powertrain management, however, it became even more prominent with the addition of the Diesel Particulate Filter (DPF) and increased Exhaust Gas Recirculation (EGR), which was due to a then-new regulation that required nitrogen oxide (NOx) emissions to be reduced by 50 percent. In order to compensate for the extra duty, a larger EGR cooler was fitted to the LMM Duramax V8.
Despite the more stringent emission controls, the LMM still managed to pose an increase of 5 horsepower and 10 pound-feet of torque compared to its predecessor. Another refined bit of hardware featured on the LMM is a revised fuel injector design. While the LBZ was equipped with a 7-hole, 158-degree injector nozzle, the LMM returned to a 6-hole nozzle design with a 159-degree range.
One unfortunate similarity between the LMM and the LBZ are the infamous pistons, which are prone to cracking under heavy load.
| Type | 6.6L V-8 Turbo-Diesel |
| GM RPO Code | LMM |
| Displacement | 403 ci |
| Valve Configuration | Overhead |
| Valves Per Cylinder | 4 |
| Assembly Site | Moraine, Ohio, USA |
| Valve Lifters | Mechanical roller |
| Firing Order | 1 – 2 – 7 – 8 – 4 – 5 – 6 – 3 |
| Bore x Stroke | 4.055 in. / 103 mm x 3.897 in. / 99 mm |
| Fuel System | Direct injection with high-pressure common rail w/ Bosch CP3 pump |
| Fuel Type | Diesel |
| Fuel Tank Size: | 26 Gallons |
| Maximum Powered Speed | 3250 rpm |
| Emissions Controls | Exhaust Gas Recirculation (EGR), Diesel Oxidation Catalyst (DOC), Diesel Particulate Filter (DPF) |
| Block | Cast iron w/ deep skirt |
| Cylinder Head | Cast aluminum |
| Intake Manifold | Cast aluminum |
| Exhaust Manifold | Cast nodular iron with steel pipe extension |
| Main Bearing Caps | Cast nodular iron |
| Crankshaft | Forged steel |
| Camshaft | Steel |
| Connecting Rods | Forged Steel |
| Engine Oil Capacity | 10 qt./9.5L w/ Filter |
| Engine Mass: | Approximately 835 pounds |
| Year | Make | Model | Transmission | Power (hp / kW) @ RPM | Torque (lb-ft / Nm) @ RPM |
|---|---|---|---|---|---|
| 2007.5-2010 | Chevrolet | Silverado HD | Allison 1000 6-Speed Automatic or ZF S6-650 6-Speed Manual | 365 / 272 @3200 | 660 / 895 @1600 |
| 2007.5-2010 | GMC | Sierra HD | Allison 1000 6-Speed Automatic or ZF S6-650 6-Speed Manual | 365 / 272 @3200 | 660 / 895 @1600 |
The 6.6L Duramax LMM engine was manufactured at the GM Duramax plant in Moraine, Ohio, USA.
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