2007.5-2010 Chevy Duramax LMM Engine Parts

The LMM engine in the 2007.5-2010 Silverado 2500HD and 3500HD

The LMM is the Duramax generation GM put in the new-body heavy-duty trucks mid-2007. It carries over the LBZ long block, with its reinforced block casting, upgraded main bearing material, thicker connecting rod I-sections and larger piston pin bore, and adds increased cooling capacity, closed crankcase ventilation, a diesel oxidation catalyst and a diesel particulate filter, a more efficient variable-geometry turbo and a low-ash CJ-4 oil requirement. Underneath that is a cast gray iron deep-skirt block with cast aluminum heads, a nitrided forged crankshaft and fracture-split forged rods, 4.055 in bore by 3.897 in stroke at 16.8:1 compression. The valvetrain is overhead-valve cam-in-block with hydraulic roller lifters and four valves per cylinder, the firing order is 1-2-7-8-4-5-6-3, and the assembly weighs roughly 835 lb. Fuel comes from a Bosch common rail system running up to 26,000 psi through six-hole injector nozzles. Oil capacity is 10 quarts with the filter, and a warm engine idles near 680 rpm.

What fails and why

The pattern we see most on these trucks is fuel dilution of the oil. Late post-injection during a regeneration puts raw fuel on the cylinder walls and some of it ends up in the crankcase; past about five percent by volume it is excessive, the oil level climbs, it smells like diesel and it thins out. Short-trip trucks have it worst. Piston cracking is the LMM's hard ceiling: the six-hole nozzle pattern aims opposed fuel streams above the wrist pin and builds a hot spot there, which shows up around 600 hp or on trucks run with aggressive timing, over-fueling and heavy towing exhaust temperatures. The warning is sudden damage under load and crankcase pressure, and stock trucks rarely get there. Head gaskets on these engines are the riveted late-2006-2010 design and rarely fail on their own, but an overheat will take them out, and then you get coolant loss, a pressurized cooling system and white sweet smoke. Carbon in the EGR valve and cooler builds progressively past 100,000 miles and shows up as a rough idle, slow throttle response, a check engine light and soot in the intake.

Stock replacement vs. upgrade

For a stock truck that is staying stock, replace in kind. A minimum compression figure of 300 psi tells you whether a used long block is worth freshening. If the heads are off for any reason on a truck that tows or is tuned, the standard spec is ARP head studs with the riveted-style late-2006-2010 gasket; the A through D grades only denote thickness, so the grade is a measurement rather than a quality ladder. Oil analysis is the honest way to set a change interval, because dilution, not mileage, is what ends the oil, and a full synthetic low-ash CJ-4 is what belongs in a DPF-equipped engine. Keep exhaust temperature in check and stay off stacked or aggressive tunes and the pistons stay together. A catch can serviced on a schedule keeps crankcase oil mist out of the intercooler while leaving the factory closed-crankcase routing in place. Rocker arms, pushrods and valve springs are performance-build parts here, not a fix for a documented stock failure.

What we carry

Mahle covers the sealing side with lower engine gasket sets, timing cover gasket sets and seals, and rear main crankshaft seals. Merchant Automotive brings full engine gasket sets with and without head gaskets and bolts, oil cooler installation and seal kits, pushrods, motor mounts and glow plug kits. Alliant Power supplies head gaskets by thickness grade and side, head installation gasket kits and a belt tensioner. Head and main studs come from ARP, Gator Fasteners and XDP, and XDP also lists rod bolts, rocker arm shafts, valve bridges, harmonic balancers and camshaft and crankshaft position sensors. Pistons for this engine are listed in this group as well. PPE covers cast iron cylinder heads, valve and spring kits, billet pulleys, dual fueler kits and oil filtration. Dayco handles serpentine belts, tensioners and idler pulleys, Dorman the harmonic balancers, accessory pulleys and engine oil cooler, and ACDelco the PF2232 oil filter and 9G glow plugs. Engine oil comes from Hot Shot's Secret and Lucas Oil in CK-4 grades.

Fitment notes

Shop by engine code, not by year. A lot of Duramax engine parts are cataloged 2006-2010 for LBZ and LMM, or 2006-2016 across LBZ, LMM and LML, with glow plugs the usual example, so a listing can look right while the part is wrong for your truck. The 2007 split matters too: a 2007 Silverado HD Classic is the old body with the LBZ, and only the new-body 2007.5 trucks got the LMM. Belt routing depends on options, since regular-cab Snow Plow Prep diesels ran dual 125 A alternators on a different bracket set instead of the standard single 125 A unit. Chassis cab trucks over 10,000 lb GVWR were rated below the 365 hp and 660 lb-ft pickup calibration. Nothing here should be assumed to carry to a 2011 LML, which moved to a CP4 pump and added DEF. Run the VIN through the fitment checker on the product page when a listing range is broad.

Frequently asked questions

Why does the oil level on my LMM go up instead of down?

That is fuel dilution. The ECM injects fuel late in the cycle to raise exhaust temperature and burn soot out of the particulate filter, and some of that fuel washes past the rings into the crankcase. Above about five percent fuel by volume the oil has lost real lubricity, and short-trip driving makes it worse. Send a sample out for oil analysis and set your interval off the result.

Do I need ARP head studs on a stock Silverado 2500HD?

Not if the truck is stock and the gaskets are intact. The riveted head gasket used from late 2006 through 2010 is the best factory design and rarely lets go by itself. If the heads come off after an overheat, or the truck tows heavy or is tuned, studs with that same riveted-style gasket are the spec we build to.

How much power can the stock LMM bottom end take?

The pistons are the limiter, and the figure owners run into is around 600 hp. The six-hole injector spray pattern concentrates heat above the wrist pin, so aggressive timing, over-fueling and sustained high exhaust temperature while towing are what crack them. Power on a dyno sheet alone is not the whole story.

What oil and how much does an LMM take?

Ten quarts with the filter. The particulate filter requires a low-ash CJ-4 oil, and the factory filter is the ACDelco PF2232. Confirm the viscosity against your owner's manual, then let oil analysis tell you how long that fill is actually good for in your duty cycle.

Not sure what fits? Call the shop at the number in the header, or use the fitment checker on any product page. We install everything we sell.