LBZ Duramax: years, specs & known problems

By CarWhere Research · Updated

The LBZ is the third-generation 6.6L Duramax, used in 2006 and 2007 (Classic body) Silverado and Sierra heavy-duty pickups and identified by an 8th VIN digit of D. It is rated 360 hp and 650 lb-ft, was the first Duramax paired with the six-speed Allison 1000, and is the last one built without a diesel particulate filter.

The LBZ arrived during the 2006 model year with a strengthened block, heavier connecting rods, higher 26,000-psi injection pressure, new seven-hole injectors and a less restrictive turbo inlet feeding the Garrett variable-geometry turbo. Output jumped to 360 hp and 650 lb-ft, and GM paired it with a new six-speed Allison 1000 automatic. It ran through the 2007 "Classic" GMT800 trucks before the LMM took over in the new GMT900 body.

Because it predates the diesel particulate filter, the LBZ is often singled out as the most desirable used Duramax. Its documented weak points are pistons that can crack across the wrist-pin area, mostly on heavily modified engines, turbo vanes that stick from carbon and corrosion, and a plastic-impeller water pump.

LBZ Duramax at a glance

GM 6.6L Duramax LBZ V8 turbo-diesel (RPO LBZ): model years, fuel and peak GM-published output
EngineModel yearsFuelPeak hpPeak torque (lb-ft)Documented problemsRecalls
GM 6.6L Duramax LBZ V8 turbo-diesel (RPO LBZ)2006–2007Diesel36065030

CarWhere lists 3 documented problems and 0 NHTSA recalls for the LBZ Duramax, each with a source. Part of the 6.6L Duramax family.

LBZ Duramax specifications

LBZ Duramax: design facts (2006–2007)
SpecificationValue
Displacement6.6 liters (403 cu in), 90-degree V8[2]
Bore × stroke103 mm × 99 mm (4.06 × 3.90 in)[2]
8th VIN digitD[2]
Compression ratio16.8:1[1]
BlockDeep-skirt cast iron with added webbing at the main bearings and taller main caps[1]
Fuel systemBosch common rail with CP3 pump, up to 26,000 psi; larger seven-hole solenoid injectors[1]
TurbochargerGarrett GT3788VA variable-geometry with a larger, less restrictive inlet[1]
Emissions hardwareEGR and diesel oxidation catalyst; no diesel particulate filter[1]
TransmissionAllison 1000 six-speed automatic (first Duramax with it)[1]

LBZ Duramax horsepower and torque by year

LBZ Duramax: GM-published horsepower (hp) and torque (lb-ft) by model year and application
Model yearsApplicationHorsepower (hp)Torque (lb-ft)Source
2006–2007Silverado/Sierra HD pickup360 hp at 3,200 rpm; 650 lb-ft at 1,600 rpm360650[1]

"—" means we could not confirm the figure from a primary source.

Which GM vehicles have the LBZ Duramax?

GM models and model years offered with the LBZ Duramax
ModelModel yearsNotes
Chevrolet Silverado 2500HD / 35002006–20072007 Classic body
GMC Sierra 2500HD / 35002006–20072007 Classic body
Chevrolet Kodiak / GMC TopKick2006–2007Medium-duty option LPD, reduced rating

LBZ Duramax problems and what to check

Cracked pistons (mostly modified engines) (2006–2007)

Major repair

LBZ pistons use wrist-pin bushings and a thinner pin, and they can crack along the centerline below the pin. Most reported failures involve larger injectors, bigger turbos or aggressive tuning, though some stock engines have also been reported.[1]

Symptoms

  • Misfire
  • Excessive crankcase blow-by
  • Smoke

Check before buying

  • Ask whether the truck has been tuned or has upgraded injectors or turbo
  • Check blow-by at the oil fill with the engine running
  • Consider a compression or leak-down test on a high-mileage truck

Sticking turbo vanes (2006–2007)

Minor

Corrosion and carbon can seize the unison ring in the variable-geometry turbo, causing poor boost control. Cleaning or rebuilding the turbo is the usual fix.[1]

Symptoms

  • Sluggish or surging boost
  • Overboost or underboost codes

Check before buying

  • Scan for boost-related codes
  • Test-drive under load and watch for erratic boost

Plastic-impeller water pump (2006–2007)

Minor

The LBZ was the first Duramax with a plastic impeller pressed onto a steel shaft. It can slip and cause cruising overheating, though most pumps reach 150,000–200,000 miles and usually fail at the seal.[1]

Symptoms

  • Temperature creeping up at highway speed
  • Coolant weeping from the pump weep hole

Check before buying

  • Look for coolant traces at the pump
  • Ask whether the pump has been replaced

Related GM research

Confirm a vehicle really has the LBZ Duramax.

Engine and transmission RPO codes are recorded against the VIN. The CarWhere build sheet decodes a Chevrolet VIN into the factory-ordered option codes on record — engine, transmission, axle and packages. $9.99, instant.

Chevrolet build sheet by VIN

Frequently asked questions

What years is the LBZ Duramax?

The LBZ was used in 2006 and 2007 Silverado and Sierra HD pickups, including the 2007 Classic models. Early 2006 trucks still had the LLY.

How do I know if my truck has an LBZ?

Look for a D as the 8th VIN digit and RPO code LBZ on the glovebox label. A six-speed Allison is another clue, since the LLY used a five-speed.

How much horsepower does the LBZ have?

GM rated the LBZ at 360 hp at 3,200 rpm and 650 lb-ft at 1,600 rpm.

Why is the LBZ considered the best Duramax?

It combines a stronger block and rods and the six-speed Allison with an emissions system that has no diesel particulate filter, so there is less aftertreatment to maintain.

What are common LBZ problems?

Cracked pistons on heavily modified engines, sticking turbo vanes, and a plastic-impeller water pump are the documented weak points.

Sources

Ratings are GM-published figures as cited; descriptions are CarWhere’s own summaries of the sources below. Repair costs appear only where a source states them and vary by shop and region.

  1. Duramax History, Lesson 3: LBZ — Drivingline
  2. A Brief History Of Duramax Engine Specs — Diesel Army

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Independent reference compiled by CarWhere — not affiliated with or endorsed by General Motors. Chevrolet, GMC, Cadillac, Corvette, Duramax, Vortec and the model names are trademarks of their owner.