GMC/Chevrolet Diesel

Related Topics:

Duramax LB7 Specs

Duramax LBZ Specs

Duramax LLY Specs

Duramax LML Specs

Duramax LMM Specs

Common Duramax Problems














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Duramax Diesel Buyers Guide

Buying a Used Duramax








When the Duramax was introduced in 2001, it was a significant improvement from the 6.2L/6.5L Detroit engines. The engine was competitively powerful, offered acceptable fuel economy, and over the years has proved itself to be a reliable competitor in the marketplace. Unlike Ford & Dodge diesels, all GMC/Chevrolet HD pickups use an independent front suspension to provide a smoother ride and tight turning radius. These trucks have been offered with every bell and whistle imaginable, and the Duramax, Allison combination has become extremely sought after. If you're in the market for a used Duramax, take a look at the model year breakdowns below.





2001 - 2004 GMC Sierra, Chevrolet Silverado


The Duramax diesel was introduced for the 2001 model year. The first generation Duramax was dubbed the LB7. Horsepower and torque peaked for the LB7 in 2004, generating 300 hp and 520 lb-ft. The lack of emissions equipment allowed the 2001-2004 model pickups to achieve respectable fuel economy, and the trucks are reliable overall. GM was forced to recall the injectors for these engines due to a considerable number of problems, but this is not a serious concern for prospective buyers since most owners followed GM's protocol and had them replaced under warranty (though this is something that should be verified by buyers). A manual transmission was optional for these model years, though the 5 speed Allison 1000 automatic was a more popular selection.







2004 - 2006 GMC Sierra, Chevrolet Silverado


For 2004, the LLY was introduced alongside the LB7 before replacing it indefinitely. 2004 - 2006 models offered suffered from overheating issues while towing. The aftermarket has responded with a variety of fixes, though buyers should be aware of the issues when searching. For 2006, the LLY underwent many changes, including a stronger cylinder head design, newly designed fuel injectors, a new VGT turbocharger, reduced engine noise, and performance was boosted to 310 hp and 605 lb-ft. For 2004 models, the 5 speed Allison automatic was available, while the Allison 1000 was upgraded to a 6 speed unit in 2005 (the 6 speed version being more desirable).




2006 - 2007 GMC Sierra, Chevrolet Silverado


The LBZ was introduced for 2006, eventually phasing out the LLY. With it came a huge leap in performance, offering 360 hp and 650 lb-ft. The 6 speed Allison 1000 automatic or a 6 speed manual transmission was available mated to the engine. The 2006-2007 model year pickups did not have any major reliability concerns and simply continued the progression of the Duramax engine family.





2007.5 - 2010 GMC Sierra, Chevrolet Silverado


Midyear for the 2007 model year, GM launched the LMM Duramax. The goal of this engine was to meet strict emissions regulations, while offering up a small performance increase as collateral. The LMM produced 365 hp and 660 lb-ft. Fuel economy suffered dearly, caused by the adoption of a diesel particulate filter and active regeneration. To be fair, both Dodge and Ford trucks experienced similar complaints regarding poor fuel economy for the same reasons. Beyond that, the trucks are reliable and the DPF's are not typically prone to clogging issues.





2011 - Current GMC Sierra, Chevrolet Silverado


The Duramax became more complicated for 2011 to meet even stricter emissions. There seem to be no major reliability concerns. The trucks employ SCR (selective catalytic reduction) technology with the use of DEF (urea) injection in order to combat NOx emissions. A 5 gallon DEF tank is required to remain filled, though the use of exhaust aftertreatments actually helped the 2011+ model trucks achieve an 11% + increase in fuel economy versus the 2007.5 - 2010 models. These trucks transmit 397 hp and 765 lb-ft of torque through a stronger-than-ever Allison 1000 6 speed automatic (a manual transmission is no longer optional). The engine blocks and internals were also beefed up to handle the additional power, and the trucks are biodiesel B20 compatible.


Additional Notes:

• If the price is right, look past the overheating issues of the LLY, but be prepared to invest in upgrades if you plan on doing a lot of towing.
• The 2001 - 2004 model years are great on fuel, have the least emissions components, and shouldn't give you any problems if the injectors were replaced under warranty.
• Avoid the 2007.5 - 2010 model year trucks if you are concerned with fuel economy. The DPF can be removed, but this technically renders the truck illegal for highway use. If you come upon an offer you can't refuse, there are some options for improving fuel economy.
• 2001 - 2007 model years are great if you're looking for a truck to tinker with. There is lots of aftermarket support, the engines are relatively simple, and there are many around. If you are prepared to enhance performance, be prepared to address any common issues such as overheating.
• Always make sure the engines have been well maintained - common rails can be sensitive to neglect.