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Thread: Pros & Cons of Servicing/Owning the LB7, and a little history.

  1. #1
    Join Date
    Feb 2000

    Post Pros & Cons of Servicing/Owning the LB7, and a little history.

    The above image is of the LB7 first-gen Duramax 6600 in my 2001 2500HD GMC SLE crew-cab. I bought this truck brand new in December of 2000 from our local GMC dealer with just 17 miles on the odometer. Negotiated out-the-door price at the time was $39k. This was the first and only Duramax on their lot. As of late December 2023, the truck has accumulated 155K miles. I have some experience with the first-gen Duramax.

    Pros & Cons of Servicing/Owning the LB7... Let's begin with what I've heard about the:


    1- Changing injectors can be a bit more complicated on the 2001-2004.5 LB7 when compared to the 2004.5 LLY and newer engines.

    2- The stainless-steel injector cups have always been considered a negative to owning or buying the first gen LB7 Duramax 6600 because they may add another potential for complication.


    1- I saw a Youtube video last year that profiled a pretty nice LB7 Duramax/Allison powered 2004 Chevy 2500HD. The video producer paid $800 for that truck because it needed head gaskets and injectors. In short, the first gen Duramax powered trucks are cheap. That truck might have been worth $10,000 in perfect condition, but they are so-so cheap when there's a problem with the engine. It's a great time to score a great deal on one of these trucks. The things to watch out for are rusty trucks coming from the rust belt of the US.

    2- The injectors made for the LB7 are less expensive than those used in newer engines, and prices continue to come down.

    Conclusion: Should anyone consider purchasing an LB7 (2001-2004) Duramax 6600?

    After having successfully removed and re-installed 16 injector cups, I now know that proper injector cup installation is not difficult. You just have to have the right information to help you remove and then re-install the LB7 injector cups correctly the first time.

    Yes, replacing injectors is a bit more complicated on the LB7, primarily because you must first remove the upper valve covers, but with the improvements in LB7 injector technology and design, these engines can go a long-long way between injector service. As a result, replacing all eight injectors will require a bit more time than it might on an 2004.5 model year LLY or newer Duramax. However, working on an LB7 is pretty straightforward. It's not difficult if you have the right information, and doing the work yourself will cut the service bill in half.

    Just about anyone who has some mechanic skills can replace the LB7 injectors. The Service Guide linked below walks you through the process step by step. Before I replaced the head gaskets in two LB7's, I tended to agree that the newer engines could be a better choice when looking at a used truck to buy. However, with two head gasket projects now in the rear view mirror, I am convinced the LB7 could offer the best value in trucks 10 years old and older. Servicing the injectors and injector cups should not be a deterrent to buying a first-gen Duramax 6600. The decision concerning whether to buy an early Duramax powered truck should be about overall condition, not just whether it's an LB7.

    No fail service for injector and head gasket replacement:

    Contact me if you have any comments or questions: Send Message
    Last edited by More Power; 12-07-2023 at 16:05. Reason: add to

  2. #2
    Join Date
    Feb 2000

    Smile 7-11-2023 - LB7 First-Gen Design Advantages, and a Little History!

    n terms of automotive engineering, the first generation of a new engine can have the least compromised design - if the development was done correctly. The LB7 is a prime example of engine development done right. The engineering team had years to develop the design of the Duramax 6600 and perhaps just as importantly, accumulate more than a million miles in real-world testing before the first truck was sold to the public.

    For example, I know that the Duramax 6600 began as a theoretical design on a dinner napkin in February of 1996. By early 1998, Isuzu had carefully assembled about 2 dozen brand new Duramax 6600 test engines in Japan, and shipped them to GM Powertrain's Romulus Engineering Center in Michigan for evaluation. These engines were quickly built into a similar number of GMT-400 (1990s body style) trucks that would then roam various regions of the US and Canada for nearly a year - testing the engine's ability to deal with extreme heat and the extreme cold, while delivering a class-leading level of performance.

    Since 2004, when produced the first Duramax 6600 conversion, I've been asked many times if the Duramax 6600 fits into the 1988-98 pickup truck chassis. I learned when assembling the Duramax conversion for Lil Red, that the Duramax 6600 was, in fact, designed for the GMT-400 (1988-98 C/K body style). The engine fits with only minor modifications. It's nearly a "drop-in". Isuzu (and GM Powertrain) didn't have a "NBS" New Body Style (1999-2007) 2500HD truck to test the engine in 1998, so the packaging of the Duramax simply had to fit into the outgoing body style to allow any on-road testing to occur. How do I know this? - One of our active members during that time was one of those GM engineers who produced prototypes for GM. Cool job!

    All this pre-production effort included maximum stress-testing the powertrain during the hottest part of summer in the Southwest US and dealing with a brutally cold winter found in Fairbanks AK in January - yes, real winter... By the way, GMPT learned that the Duramax needed help to run warm enough during that winter in Fairbanks. This experience gave the engineers the information they needed to develop the hardware and software that was necessary to deal with the extreme cold. This is why, in part, the very first LB7 equipped trucks were shipped to dealers in the fall of 2000 with a factory "winter front". The design ethic at the time was that there be "no dissatisfied Duramax owners". The Duramax 6600 simply had to exceed expectations.

    Over a 3 year period during this development and introduction phase, I spoke to a few tens of associated people from Isuzu, DMAX and GMPT. I had access to the engine design team, vehicle prototype engineers, GM Powertrain engineers, DMAX engine manufacturing, Allison engineering/marketing, GM marketing and advertising and even the management leadership at both GMPT and DMAX. Everyone was open and available, always answered all of my questions, showed me everything I asked to see and they inspired my confidence in the Duramax 6600. They were serious about this project, and they were proud of their new diesel - had every right to be.

    The design of the brand new Duramax 6600 was mature enough by the fall of 1999 to allow GMPT to ship 2 prototype Duramax/Allison equipped GMT-800 trucks (1999-2007 body style Chevy/GMC) to Montana for me to test drive. These trucks were accompanied by 2 GM Powertrain engineers, 2 GM marketing people and a couple of others who were there to solve any problems that might come up. At this point in time, engine production wouldn't begin for another 9 months and production models wouldn't be available to consumers for another full year. You can read more about that truck evaluation here: (Notice the build date written on the rear differential in the photo I took for that article). Outside of GM and Isuzu, I was the first to drive a Duramax 6600 powered pickup truck.

    I've uploaded the article for the Duramax 6600 Performance Pull-Off from October of 1999.

    Then, early that next year (early 2000) GM Powertrain launched what became known as the Duramax Diesel Power Tour. I encourage you to visit the following link to learn more about how GMPT continued testing and promotion of their new diesel power-train. What's interesting to note here is that this very same Power Tour attended's 2000 Rendezvous on our property here in Montana (annual gathering for members) in July of 2000. Everyone who attended got to see the new truck and the Duramax months before any dealership had one in stock. We had a number of dealership people and automotive writers attending that Rendezvous in 2000, just get a first (for them) look. That new truck and 50' 20,000-lb trailer (and the crowd it drew) caused quite a stir in our neighborhood (see above).

    No diesel engine produced or used by General Motors in their light trucks ever received more durability or performance testing prior to being sold to the public. And in fact, none of the later generations of the Duramax 6600 were tested so rigorously.

    Yours truly became the first automotive writer to tour the DMAX engine production facility in Moraine Ohio - in early 2001. They showed me everything, and in addition to articles for our web site I also wrote a series of articles for Truck Trend magazine (see above) about both the Duramax and DMAX Ltd. during that time frame. That visit in early 2001, and meeting all of the company principles, created a level of trust that ultimately resulted in them inviting our entire TDP member group to tour the engine plant later that summer (and GEP - General Engine Products - a subsidiary of AM General, their 6.5TD engine plant located in Franklin, OH). See the lead-in photo at the top of this post, taken in front of the DMAX Ltd engine production facility in Moraine Ohio... This was huge, and a really big deal. Something like this had never been done before - or maybe since... In the days following the plant tour, representatives from Allison and GMPT attended and spoke during our 2001 TDP Rendezvous seminar period - that occurred in the Dayton, OH campground that our group had more or less taken over. Everyone attending got to personally meet and talk with those who were largely responsible for the new 2500HD/3500 trucks/diesel powertrain. Simply huge! I was then and I remain so grateful. There's still a lot more to talk about, but this is enough for now...

    As the years have slowly ticked by since that introductory period, we've learned that complying with the EPA's ever more demanding emissions regulations has a cost, in large part through an ever expanding list of emissions control software and hardware... Not surprisingly, unburdened by the majority of what would befall later generations of the Duramax 6600 in terms of emissions compliance, the LB7 solidly claims the fuel economy title among all of the various generations of GM's flagship diesel that have been developed through the years. The original LB7 was not burdened with the emissions equipment that later models were/are saddled with, and this allowed the LB7 to produce better fuel economy. Even when tasked with towing huge loads in the desert Southwest here in the US, the LB7 didn't overheat. The newer models (with ever larger EGR systems) had to incorporate a larger engine oil cooler, larger radiator and larger fan assemblies to cope with the increased heat load that the EGR cooler puts into the engine. The later engines saw an increase in power, which was necessary in part, to maintain towing performance in extreme conditions. In other words, later engine design changes were more about compensating (compromising design) for emissions control (and advertising) than any real-world improvement in performance. A well-kept first-gen LB7 Duramax can, even today, tow monstrous loads in the high heat of summer without overheating or be found lacking in power. And, a smart use of power enhancers (that produce no/little smoke) used with the LB7 today won't alarm the EPA gate keepers - even when installing performance oriented intake and exhaust systems, the way it absolutely will in any DPF/DEF equipped Duramax powered pickup truck.

    The 2001 LB7 48-state emissions regulations did not require EGR, a catalytic converter (diesel oxidation converter) or any other exhaust aftertreatment - one huge plus for the 2001 LB7. My 2001 GMC D/A didn't come from GM with any factory emissions control hardware (i.e. EGR or exhaust system cat/DPF/DEF) - oh, the good old days...

    So... as long as the truck is nice otherwise, the LB7 shouldn't be left off the table when considering whether to own/buy/keep one.

    Jim Bigley
    Last edited by More Power; 08-31-2023 at 11:46. Reason: add pics & stuff

  3. #3
    Join Date
    Feb 2000

    Thumbs up 8/21/2023 - Power Tour at our 2000 TDP Rendezvous

    Duramax Diesel Power Power Tour attended's 2000 Rendezvous on our property here in Montana (annual gathering for members) in July of 2000. That tour truck caused quite a stir in our neighborhood! Fun times! Click the link to learn more about Power Tour here in Montana.

  4. #4
    Join Date
    Feb 2000


    As promised, I've uploaded the article for the Duramax 6600 Performance Pull-Off from October of 1999.

    The linked article covers the performance testing we ("we" - myself, another automotive writer and full logistical support from GMPT and the local Chevrolet dealership) did for these trucks right here in Montana. The testing we performed here in Montana included performance/drive-ability evaluations using a 10,000-lb trailer on a long 6% grade from a standing start - among several other tests. We also performance-tested/compared these prototype trucks against a new Ford Powerstroke and a new Dodge Cummins. This is the very first-ever non-GM test of the Duramax 6600 powered pickup trucks.

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