2006 GMC GMC Sierra 2500 HD

Reliability tier: verified - see /disclosure/

Engine: 8.1L V8 Gasoline (Vortec 8100, L18) (GM Vortec big block, 8.1L), 2v

Vortec 8100 L18 (VIN G): GM Gen VII big-block V8, 8.1L (496 cid), OHV 2-valve, cast-iron block AND heads, sequential multiport fuel injection (PFI, no DI), ~9.4:1 compression, no cylinder deactivation; 340 hp @ 4,200 / 455 lb-ft @ 3,200 in the HD pickup ratings (some sources list ~330 hp / 450 lb-ft for portions of the run - year books differ, verify per VIN when it matters). Paired with the Allison 1000 or 4L80E/4L85E (context only - engine platform). The big-gas option alongside the Duramax in the HD lines.

Applicable failure modes (4)

• Exhaust manifold bolt breakage (cold-start tick)
• Hard cold start / fuel delivery wear
• Ignition service at mileage: coils, wires, plugs (misfire under load)
• Valvetrain / lifter noise on the 8.1L (often mistaken for piston slap)

Applicable parts (12)

• 8.1L Vortec EGR Valve (OEM)
• gm-hd-gas-vortec: exhaust-manifold-bolt (honest catalog gap)
• gm-hd-gas-vortec: exhaust-manifold (honest catalog gap)
• 8.1L Vortec Fan Blade (OEM)
• 8.1L Vortec Fan Clutch (OEM)
• 8.1L Vortec Fuel Injector (OEM)
• GM HD In-Tank Fuel Pump Module 2004-2007 (OEM)
• GM Truck V8 Ignition Coil (shared 4.8-8.1 line) (OEM)
• 8.1L Vortec Spark Plug (OEM)
• 8.1L Vortec Spark Plug Wire Kit 2003-2007 (OEM)
• 8.1L Vortec Thermostat (OEM)
• 8.1L Vortec Water Pump Kit (OEM)

Platform recipes (3)

• Cold-start tick on a 6.0L or 8.1L GMT800 HD gas truck: find the leaking manifold flange before blaming lifters or injectors, then extract the sheared studs and refit bolts and gaskets (mode fm-gvg-exhaust-manifold-bolts)
• Hard-cold-start path (fm-gvg-fuel-delivery-cold-start): the owner record puts most cases on tired in-tank pumps and rail pressure bleed-down, not ignition
• Ignition service path (fm-gvg-ignition-misfire): misfire under load / rough idle at mileage on the 2001-2007 HD gas engines

Recalls that include this truck (1)

• 06V-289 (August 3, 2006) - ENGINE AND ENGINE COOLING: ON CERTAIN TRUCKS EQUIPPED WITH AN 8.1L V8 (RPO L8-VIN G) ENGINE HAVE A CONDITION IN WHICH THE ENGINE FUEL RAIL PULSE DAMPER RETAINER CLIP MAY FRACTURE RESULTING IN INADEQUATE RETENTION OF THE DAMPER.

Matched by the model and model year NHTSA lists for each recall - a recall often covers only part of a year's production, so read its text for the build dates and versions it names. Whether a recall is still open on your VIN is not known here; check nhtsa.gov/recalls. All recalls, investigations and bulletins for this engine: /recalls/gm-hd-gas-vortec/

Reference for this truck