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The LBZ Duramax is considered to be one of the most legendary engines in the diesel pickup truck world. Even though it was produced for such a short time, it is referred to by many as the “Holy Grail” of GM diesel engines.
If you’re looking to purchase a used Chevrolet Silverado or GMC Sierra, knowing the LBZ Duramax engine year can help you obtain an excellent used truck that is pre-emission and a strong, reliable performer.
This complete guide will provide you with all the information you need to know about this famous engine.
The LBZ Duramax was produced for only two model years, which were 2006 and 2007. The LBZ was introduced in late 2005 for 2006. It was the replacement for the ill-fated LLY generation.
Production ended midway through the 2007 model year when the new LMM generation commenced production to meet increasingly stringent federal emissions regulations. Because of the short production run, trucks equipped with the true LBZ engine are rare, very desirable, and provide a greater resale value than nearly every other diesel truck.
The primary reason for diesel enthusiasts to stockpile LBZ trucks is straightforward: it embodies the pinnacle of Duramax horsepower before the imposition of sophisticated emissions controls by governmental legislation.
GM was legally mandated to install DPFs starting with the LMM series in mid-2007. It has added DEF systems since that time.
While these technologies are intended to minimise environmental impact, they also substantially limit exhaust flow, reduce fuel efficiency, and create numerous high-cost failure points. The LBZ only has a relatively simple EGR system and catalytic converter, resulting in no restrictions on the exhaust system.
GM didn’t merely ignore the emission control systems; they redesigned the entire 6.6L engine structure, from the old LLY Engine block to the LBZ Engine block. LBZ Engine block changes are:
2006 saw an enormous milestone in the progress of a driveline product. The 6-speed Allison 1000 auto trans was now mated to the Duramax for the very first time. Previous years had only been available with a 5-speed version.
By adding one more gear ratio, the engine had lower RPM’s on the highway, thus providing better fuel economy and cooling while hauling heavy loads.
The mechanical upgrades allowed GM to safely crank up the power straight from the factory floor.
| Feature | Specification |
|---|---|
| Production Years | 2006,2007(early) |
| Configuration | 6.6L V8 Turbo Diesel |
| Horsepower | 360 hp@3,200 RPM |
| Torque | 650 lb- ft@ 1,600 RPM |
| Fuel System | High-Pressure Common Rail via Bosch CP3 Pump |
| Turbocharger | Garrett Variable Geometry Turbo (VGT) |
| Transmission | 6 Speed Allison 1000 Automatic |
If you’re looking for a used LBZ, several common issues can crop up:
The LBZ uses a factory water pump that has a plastic impeller. After years of use, the plastic will break and/or strip off the steel shaft of the water pump. When the water pump no longer pumps coolant properly, the engine will quickly overheat. The solution is to replace the plastic impeller with a welded steel impeller.
Factory transmission lines consist of a mixture of metal tubing and rubber hoses connected with crimped fittings, which deteriorate and leak fluid after going through numerous cycles of heat. Many owners choose to replace them with heavy-duty aftermarket braided lines.
The LBZ in its stock form is not known to crack pistons very often, but many owners exceed the limits of the stock block. If you load a heavy tune on these engines and exceed 600-650HP with stock internals, the cast aluminium pistons will likely crack due to excessive cylinder pressure.
A frequent problem with electricity occurs near the alternator bracket. The main engine wire harness can rub on the sharp metal edge. With time, vibration can wear away at the insulation. This creates electrical shorts, blown fuses, and intermittent engine diagnostic trouble codes.
GM offered trucks with mechanically identical engines but was sold with “detuned” maps from the factory during the beginning of 2006. This was also referred to as a “2006 LLY engine.” To know whether you have a true factory full-power original LBZ engine, you need to locate the 8th character of your vehicle’s VIN:
Always check the truck’s physical VIN plate on the driver’s side dashboard.
You can help ensure your 2006-2007 Duramax can run over 300,000 miles with just a few small modifications to an original, clean, and unmodified engine.
The CP3 high-pressure pumping system pulls the fuel from the tank entirely. It produces enough vacuum to introduce air into the fuel system. By adding a fuel lift pump (FASS or AirDog), you will be able to deliver consistently clean, pressurised fuel from the tank to the engine, preventing premature wear of your fuel injectors.
LBZ is equipped with an EGR valve to feed previously burned exhaust fumes back into the fresh air intake system. Over time, this leads to the accumulation of carbon and muck on the inside of your intake tract. Periodically cleaning and servicing your EGR system will help maintain a clear top end for your engine.
The factory steering tie rods on heavy-duty Silverado and Sierra chassis are known for being weak. They can be fairly thin and can easily bend when put under a lot of pressure. Upgrading to heavy-duty tie rod sleeves is a much cheaper alternative to strengthening the front-end steering assembly.
The 2006 and 2007 LBZ Duramax are legendary machines thanks to their heavy-duty engine block, 6-speed Allison Transmission, and tremendous tuning potential without the complex headaches of modern-day diesel emissions components.
A well-maintained LBZ is still one of the best investments you will ever make in a truck, despite their high market price and usually very high mileage.