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Learning Diesel Trucks


We do that 10 times a week and been doing it for a long time, so here we share with you a very simple procedure for a quick health check that applies to any diesel truck.

1.- Cold start idle, start the truck while cold,  listen for knocks or rough idle.

2.- Smoke, check the exhaust for any smoke coming out, not all smokes are bad, but white smoke is bad, could imply many different problems, some very expensive.

3.- Blow by, check the oil cap or dip stick for air pressure coming out, which implies compression inside the engine and worn out piston rings, some blow by is normal, but a lot means the truck is toast.

4.- Coolant check, check for compression inside the coolant deposit, also diesel or oil in the coolant is a sign of something bad going on.

Aside for any other things you might want to check, checking these points takes 3 minutes and provides a lot of information on the trucks health bill.


These days you can find a ton of information online about what is best for each use, however at the prices used diesel trucks are selling these days, the answer is very simple, if you use the truck simply to drive yourself around town, you're better off in a Prius never mind a gas truck... however if you use your truck to haul trailers or heavy loads theres is nothing better than a diesel and overtime it will pay for itself in fuel savings and will provide you with lots of power as well as durability and reliability. So simply put... DIESEL IS BETTER.

s far as which diesel is better,  well thats a tough question, one that has many answers with most of them being right, so if you grew up around Chevys that might be the best for you, if you have a Cummins 18 wheeler then the Dodge is the best for you, and if your dad had a Ford F100 then you only buy Fords. In the end they are all good as long as you know the details, so here they are:

Chevrolet GMC Duramax Engines

Despite what you see on the streets, work sites and drag strips of America today, General Motors diesel engine hasn’t always been treated with affection by its owners and with respect (even if somewhat reluctantly) by its competitors.


Today’s Duramax engines are recognized as dependable, powerful engines capable of being enhanced by internal engine modifications as well as bolt-on technology. They are used for towing and hauling, frequently over long distances and through unforgiving environments. They are asked to perform at the highest level and be ready to go at it again and again. Like other diesels, they are easily capable of traveling half a million miles – with proper attention and maintenance, of course.

But the 6.6L Duramax found in today’s Chevy Silverados, GMC Sierras, Chevy Express and GMC Savannas (as well as countless other trucks and even cars of a more vintage nature) is a long way from the diesel engines GM tried to bring to market originally.

According to Roy Berndt, engine expert and Engine Builder contributing editor, GM faced an uphill battle to competing in the diesel arena.


“In 1996, as General Motors was finalizing plans for its next generation of full-size trucks (code named GMT800), the company had only 3% market-share of the diesel-powered heavy-duty pick-up truck segment,” says Berndt. “This was really no surprise, since GM had single-handedly alienated the American buying public against the diesel engine beginning back in the late ’70s and early ’80s with the 5.7L V8 and 4.3L V6 diesel engines that were, let’s just say, ‘less than stellar.’ While there’s no point now in rehashing mistakes of the past, the 6.2L and 6.5L diesels had continued on in a similar tradition, even though the 6.5L was used in the HUMVEE for the military.”

The 6.2L and 6.5L diesel engines of the late ’80s were really no match for the Cummins 6BT diesel found in the Dodge Ram in 1989 nor the Ford/International Power Stroke available from Ford in 1999. Partnerships between the other vehicle manufacturers and their engine suppliers had effectively neutered GM’s diesel program and by 1999, GM didn’t even offer a diesel engine in any of its mid-size trucks.

However, behind the scenes, GM and Japanese engine maker Isuzu were working on a joint venture intended to produce a truly modern diesel engine. The collaboration created DMAX Ltd. “The name signified the diesel engine and maximum power, cleanliness and fuel economy,” says Berndt, “and the 13 hour time difference between Japan and the U.S. worked to their advantage.” Teams could videoconference late in the day for one team, early for the other, working on issues while the other team slept.


The new engine that resulted from this joint venture was a 6.6L, 90-degree, direct-injection, overhead valve, four-valve-per-cylinder, turbocharged diesel V8 with aluminum high swirl cylinder heads. An innovative electrically controlled common-rail fuel system provided maximum power for each pulse of fuel used and allowed full authority in injection timing and quantity. This combination along with pilot injection provided operating quietness and smoothness typical of similarly sized gasoline engines.

“When it came time to decide upon the marketing name for the new engine, GM was already handicapped by its poor diesel reputation,” Berndt explains. “The name itself was critical, as it would compete against Ford’s established ‘Power Stroke’ diesel engine. Dodge was using the Cummins engine and needed no other name, so after many meetings the engine was named Duramax Diesel 6600. Like the joint venture name, ‘Duramax’ was meant to highlight the durability and reliability of the new engine.”

In late 2000, the Duramax Diesel 6600 debuted in the new 2001 HD pickup trucks. Brought to market in only 37 months, it was the fastest new engine developed by GM Powertrain to date. The engine was an immediate success, making Ward’s “10 Best Engines” both in 2001 and 2002, and bringing up GM’s market share from 3 percent to 30 percent in the HD Diesel pick-up truck market.

The Duramax Evolution

Since its introduction, there have been multiple generations of the Duramax engine platform, all based on the original 6.6L design. They are all still relevant in the aftermarket.


The LB7 Duramax was first introduced for the 2001 model year in the Chevrolet Silverado HD, GMC Sierra HD, GMC TopKick (medium duty) and Chevrolet Kodiak (medium duty) trucks. That year also brought the Allison 1000, arguably the first automatic transmission in its class worthy of being mated to a powerful diesel. The LB7 was the pioneer of common rail technology, as Dodge would not introduce its own common rail Cummins until the 2003 model year – Ford wouldn’t add it to the Power Stroke until 2008.

The LB7 is a favorite engine, dramatically different from other Duramax models – it predates emissions regulations. As such, it’s praised for reliability and has been regarded as a particularly economical variation of the engine.

As impressive as GM’s new engine platform appeared, however, the LB7 had terrible problems with fuel injectors failing. In fact, injector failures were so frequent that GM was forced to recall the poorly designed units and replace them with an updated design. In order to provide loyal customers with a sense of reassurance, the factory warranty was extended to cover the new injectors for up to 200,000 miles.

“The integrity of the engine was great,” explains Engine Builder contributor and diesel expert Bob McDonald. “Its biggest problem was the fuel system, and particularly, injector failure. The engine used the Bosch common rail fuel system, which included the high-pressure fuel pump, high-pressure fuel rail, hard lines, injectors and electronic control module. For some reason, the Bosch injectors could not survive in the Duramax and would fail in three different ways – all related to the injector’s body becoming cracked.”

McDonald explains that one symptom of a cracked injector is excessive white smoke coming from the tailpipe, generally most noticeable at idle, especially while sitting in traffic. Fuel is entering the combustion chamber at the wrong time, causing the white smoke, showing an unburned fuel condition.

Fuel leaking into the combustion chamber, cannot be controlled by the engine’s ECU. Known as an injector’s balance rate this can be seen with a scan tool. The balance rates of an injector are adjustments of fuel to the injector made by the ECU, adjustments made from fluctuations of the crankshaft detected by the crankshaft position sensor.

The balance rates are given by the value being a plus or a minus to the volume of fuel per cylinder. If there is too much fuel for a particular cylinder, the balance rates for that cylinder would be a minus. The ECU then tries to take fuel away to correct the imbalance condition. White smoke indicates this minus balance rate caused by a cracked injector.

Another symptom of cracked injector failure is fuel dilution of the engine oil. This is due to an injector’s body being cracked externally, causing fuel to leak into the crankcase.

The injectors of the LB7 were located under the valve cover. The hard lines went from the high-pressure fuel rail and through the valve cover. If the injectors were leaking externally, fuel dilution could happen fairly quickly and go unnoticed because the engine would continue to operate fine.

There have been cases or injectors leaking externally so badly that the crankcase had filled with so much diesel that it began leaking from the rear main seal.

The last form of injector failure was a hot-engine, hard-start condition. When the engine was cold, the vehicle would start fine and drive normally without any noticeable problems – until the owner decided to stop somewhere on the trip.

When the owner would try to restart the vehicle, the engine would spin over but never fire.

This was caused by the injector’s body being cracked on the return side. The heat from the engine would literally cause the crack in the injector body to expand further, causing the fuel pressure that was entering the injector to be returned to the fuel tank.

The vehicle would have to sit for several hours and cool down before the engine would restart.

With so many injector failures between 2001 and 2004, GM extended the injectors’ warranty from five years/100,000 miles to seven years/200,000 miles. This did not, however, remedy the problem.

The biggest problem came when customers had their injectors replaced under the seven-year/200,000-mile warranty. Then several years later, after the truck was out of warranty, the injectors failed again, which, of course angered many customers because there was still a problem and now they were going to have to pay for it. And, if the other injectors didn’t last very long, this would be an ongoing problem for the owner.

With the injectors being under the valve cover, a lot of the components of the top of the engine have to be removed in order to access them so injector replacement in the LB7 Duramax is labor intensive.

It’s always advised that if there are several injectors causing problems that it’s better to replace them all because of the amount of labor that it takes to get to the injector.

The average cost of an injector replacement on the LB7 is generally around $4,000 to $5,000. The replacement process takes between 10 to 12 hours of labor and the injectors cost around $350 each. Bosch went through several designs before there seemed to be a cure


In the middle of 2004, GM released the second generation of the Duramax, with the RPO code of LLY, with the eighth digit of the VIN designated as number 2. The LLY was GM’s first attempt to implement emissions requirements on its diesel trucks. To meet this goal GM turned to a newly developed Garrett turbocharger with a variable geometry vane system and installed an Exhaust Gas Recirculation valve. Learning from problems with injectors in the previous LB7, GM changed the valve covers to not only remove them from the engine oiling system, but allow access to the injectors without having to remove the valve covers.

There were several reasons for the change: the injectors changed design and were now on the outside of the valve covers, providing easier access, and the EPA was tightening down on emissions standards for diesel engines in order to reduce NOx gas.

The LLY incorporated the use of an EGR (exhaust gas recirculation) valve. When engine conditions would reach a certain criteria determined by the ECU, the EGR valve would open to reintorduce exhaust gas be reintroduced into the intake manifold.

This often caused a buildup of soot in the intake system because the exhaust gas displacing the oxygen meant cooler combustion; the cooler combustion inside the cylinder formed soot.

In order to reintroduce exhaust gas into the intake of a diesel engine, the exhaust gas has to pass through what is known as an EGR cooler. A diesel engine exhaust temperatures can be much higher than gasoline, reaching as high as 1,200° F.

Before the exhaust gas reenters the intake at this temperature, it has to be cooled. The EGR cooler is more or less a small radiator that is a part of the engine’s cooling system, which as the hot exhaust gas passes through the cooler will cool the exhaust gas before reaching the intake manifold.

Over a period of time, the EGR coolers will fail, causing the engine coolant to enter the intake manifold. This will often result in loss of coolant with steam emitting from the tailpipe.

The LLY suffered from overheating. When Duramax incorporated the use of the EGR cooler, the cooling system of the engine was not upgraded.

When towing with the LLY up steep grades on a hot summer day, owners often noticed that the cooling system could not sustain the engine’s temperature and would overheat.

One of the other features of the LLY was the use of a VNT (variable nozzle turbo). The VNT allowed the turbocharger to change speed by altering exhaust pulses to the turbine wheel. This created better spool time and more boost for the engine off idle and would also change spool at the turbo when the engine was at cruising speed for the use of less boost. This more or less lets the turbo make boost when there is a demand.

The VNT was sometimes responsible for the overheating issues of the LLY because of the more restricted exhaust system. Some overheating issues did result, however, in head gasket failures, which could damage the entire engine.

Early on, problems came forward from customers complaining of severe overheating, and, in some situations, blown head gaskets. Although initially GM denied that it was a problem, after it was sued by a consumer group it relented and included overheating and blown head gaskets as a warranted item.


The LBZ was relatively short-lived, available for only two model years for no other reason other than its replacement, the LMM, was introduced with the capability of meeting stricter emissions regulations coming over the horizon. Mechanically, the LBZ is nearly identical to the 2006 model year LLY but features more aggressive engine tuning, producing more horsepower and torque. The LBZ produced 360 horsepower and 650 lb.-ft. of torque to the LLY’s 310 horsepower and 605 lb.-ft. 

The block was redesigned with more integrity along with the pistons and rods for the increase in horsepower to 360 and 650 ft.-lbs. of torque. The cooling system was upgraded with the use of a bigger radiator and fan along with a bigger EGR cooler. Under the LBZ, the Bosch fuel engine management system also changed. This time, the fuel system used a new 32-bit controller along with seven hole injectors.

The fuel pressures increased from 23,000 psi to 26,000 psi. Fuel sprayed directly onto the glow plugs for faster starts. The glow plugs were also independently controlled from the use of a controller for more efficiency during cold starts.

The 6.6L Duramax LBZ’s applications included the Chevrolet Silverado HD, GMC Sierra, HD, Chevrolet Kodiak, and GMC TopKick (the Kodiak and TopKick being medium duty truck models. In the aftermarket, the LBZ is thought of the “hot rod” for its huge performance potential, abundance of support, and the fact that it is the last model produced without a diesel particulate filter. Information released by General Motors at the introduction of the LBZ state that the engine has an increased piston pin diameter and thicker connecting rod section over previous generations in addition to an improved block casting.

The block was redesigned with more integrity along with the pistons and rods for the increase in horsepower to 360 and 650 ft.-lbs. of torque. The cooling system was upgraded with the use of a bigger radiator and fan along with a bigger EGR cooler.

The LBZ was available with either the Allison 1000 6-speed automatic or the ZF650 6-speed manual transmission, though 2007 would mark the last model year that any Duramax engine was available with a stick shift. The Allison transmission also changed from 5-speed to a 6-speed. The additional gear in the transmission reduced cruising speed by 200 rpm.

Owners of an earlier LLY were able to upgrade the cooling system of their vehicles by installing the radiator and fan along with the fan shroud from an LBZ. By mid-model year for 2007, the LBZ was effectively replaced by the emissions compliant, diesel particulate filter-equipped LMM.

we usually only carry trucks up to lbz in chevy, they are the most sought after and a personal favorite of ours, so mostly we keep the ones you're looking for at a budget friendly price.