2007.5-2010 GMC Duramax LMM Cold Air Intakes

What an intake kit changes on a Sierra HD LMM

The Sierra HD left the factory with a high-capacity air cleaner as standard equipment, which is worth remembering before you shop. From the box, air passes the turbo mouthpiece into the compressor side of the water-cooled Garrett GT3788VA variable-vane turbo, out the driver-side hot pipe to the air-to-air intercooler at the front of the truck, back through the passenger-side cold pipe, and into a cast Y-bridge that splits the charge to both cylinder heads. The LMM Y-bridge also routes exhaust gas recirculation flow and carries the grid heater, so any part you add on the intake side has to preserve those connections. The closed-crankcase system vents into the intake too, which is why the inside of the tubing is always lightly oiled on a truck in good health.

What fails and why

Boots and couplers blow off or weep, and the oil film from the crankcase vent is a big part of why, because it reduces clamp grip on the pipe. Sometimes it is a bead or alignment problem letting the boot walk. What you notice is a pop and a flat pedal, or a hiss under boost with oily dirt collecting at the joint, with P0299 underboost stored. BD lists charge-air leaks among the common LMM issues and points out they get read as turbo failure. Heavy film and soot accumulate progressively with mileage, and a Sierra that idles a lot or runs short trips collects it faster, which shows up as rough idle, hesitation and haze. Pooling oil, as opposed to a film, is a reason to check crankcase pressure, the turbo and oil consumption.

Stock replacement vs. upgrade

Plenty of Sierras need nothing more than a service filter in the factory box. The reason to go to a kit is a larger, straighter tube and a sealed housing: the S&B cold air intake and the Wehrli 4-inch intake kits are cataloged for the 2007.5-2010 LMM specifically, not adapted from another year. A turbo inlet kit takes on the factory mouthpiece feeding the compressor, and the staged high-flow bundles put the intake and charge-air pipe upgrades in one box with the boots and clamps included. Those bundles keep the EGR and grid-heater connections and are built to run with no tuning, so none of this alters the truck's emissions hardware.

What we carry

Wehrli Custom Fabrication covers the 4-inch intake kits, the air-box versions, the Stage 2 and Stage 3 high-flow bundles and silicone boot and clamp kits. S&B and Banks Power supply cold air intakes, the Banks unit being the RAM-Air kit. Pacific Performance Engineering adds a carbon-fiber turbo inlet upgrade kit and cylinder head bank manifolds. Intercoolers and charge-air pipes for this Sierra live on their own page; the wider category is intakes, and all of our parts for this engine are grouped under Duramax.

Fitment notes

The split to watch is LBZ versus LMM and classic versus new body. The 2007 Sierra HD Classic is the GMT800 body with the LBZ, while the LMM came only in the GMT900 body, so year alone will not tell you which kit to buy. Work Truck, SLE and SLT share intake parts, and dually 3500HD trucks use the same pieces as single rear wheel trucks. Where it gets fussy is bundles that include intercooler piping, so run the VIN or the fitment checker before ordering one of those.

Frequently asked questions

Will an intake kit sold for an LBZ bolt onto my 2008 Sierra?

Not reliably. LBZ and LMM trucks share a lot of cold-side architecture, but these kits are cataloged by engine and body, LBZ or LMM, classic or new body. Check the engine RPO and the body before you order, especially on anything from the 2007 model year.

What comes in a staged high-flow intake bundle?

A bundle packages the intake side with charge-air hardware, and the kits for this engine include the silicone boots, clamps and the o-rings for the grid heater and EGR connections, because those get disturbed during the install. They are designed to keep the factory emissions connections and to run without tuning.

Is the factory air box worth keeping on a Sierra HD?

It is not a bad starting point, since GM fitted a high-capacity air cleaner as standard on these trucks. The reason owners replace it is the tube and housing design rather than filter area, and the LMM-specific kits from S&B and Wehrli replace both together.

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.