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2001-2007 HD Duramax Truck Review







In 2001 GM in partnership with Isuzu came out with an all new diesel engine for their newly redesigned line of pick up trucks.  This new 6.6 liter Duramax diesel engine was leaps and bounds better than the 6.5 liter diesel it replaced.  The Duramax is a 403 cubic inch (6.6 liter) V8 featuring a cast iron block, 32 valve (4 valve per cylinder) aluminum cylinder heads and high pressure common rail direct injection.  The Duramax is more reliable, more powerful and is more fuel efficient.  The Duramax is probably the quietest diesel engine on the market for the 2001-2007 model years.  The only close competition in the quiet category is the new Ford 6.7 diesel.  Because of the quieter engine, it is possible at times to order food at a drive thru without shutting the truck off.  Most diesel trucks drown out the drive thru speakers with engine noise.  The Duramax engine received a few changes between its introduction in 2001 and 2007 at the end of this body style run.  I will detail the changes later in this article.  In addition to the Duramax diesel engine, these new diesel trucks were equipped with the Allison 1000 automatic transmission unless you opted for the ZF 6-speed manual transmission.  This article applies to both the Chevrolet Silverado 2500HD/3500HD Duramax and the GMC Sierra 2500HD/3500HD Duramax as they are essentially the same truck with the only differences being name badging and slight cosmetic differences.


Like the 1/2 ton trucks, the body of the 3/4 ton and 1 ton trucks style received the same change from boxy to smooth & sleek in 1999.  Although the old body style was still in production for the 1999 model year.  Also like the 1/2 ton trucks, the front end shares a similar appearance to the Suburban, Tahoe and Yukon front ends.  The HD pick ups also suffer the rocker panel and cab corner rusting problem that the 1/2 ton trucks have.  Rust is an issue on any vehicle depending on where you live.  GMs seem to rust at the rockers more often while Fords and Dodges seem to rust on the wheel well area on the box sides.  Rust shouldn't always be a deal breaker because it can usually be fixed and is usually strictly cosmetic.  When inspecting any truck, it needs to be determined if the rust is more than cosmetic and if it is or will interfere with usage, safety or driveability of the truck.  Over all these trucks are strong, powerful and reliable.  The independent front suspension definitely offers a smoother ride than any other 3/4 ton or 1 ton truck on the market.  There are some drawbacks to the independent front suspension as well which is mainly tie rod breaking.  This problem is not an issue under normal driving conditions.  Where you will run into this problem is heavy 4 wheel drive abuse such as off roading, drag racing, mudding, truck pulling, etc.  If you will being doing any of these activities, it is recommended to upgrade the tie rod ends with stronger pieces that are readily available from several aftermarket vendors.


The interior is very similar to the 1/2 ton models.  The trucks are available with standard cab, extended cab and a 4 door crew cab.   The seats are  comfortable, the interior is fairly quiet, the dash is laid out nicely and all accessories are well located and easy to access.  Long trips in these trucks is no problem.  The cup holder in the center console of the HD models is different from the 1/2 ton models.  The cup holder section is actually turned 90 degrees to the right which places the 2 cup holders inline front to back on the passenger side of the console instead of toward the front and puts the pencil/pen storage tray on the driver side instead of facing toward the rear.  I do not understand the reasoning behind this but all of the HD trucks in this body style  are like this.  There were several interior packages offered with options in seat material, heated seats, upgraded climate control systems, Bose stereo system, available console, overhead console, integrated HomeLink garage door remote, steering wheel mounted radio controls, driver information center, moon roof and various other features and options.  More options were available after the first few years of production.  Some of the packages did get a bit confusing over the years.  For a while LT trucks had leather interior but a some point their were multiple LT packages (LT1, LT2 and LT3) and all of them had different options included and I believe leather was only included in the LT3 package.  Options for the rest of the truck is the same so make sure you research the different packages and what is included before purchasing one of these trucks.  GM was nice enough to put a sticker in glove compartment with RPO codes for the vehicle.  That sticker has a code for everything the truck is equipped with from axle ratio to seat material to engine and everything in between.  The integrated HomeLink garage door opener system which is in the front of the overhead console is a very convenient feature. The HomeLink system has 3 buttons that can be programmed to garage doors, remote lighting and just about anything else that is remote controlled. 


Just like I recommend for 1/2 ton GM trucks, I would suggest to anyone looking at these trucks to look at the models with a center console unless you need a front bench seat.  It all depends on your specific needs I guess.  The center console offers a large storage well between the seats that is lockable in most models, a smaller storage area under the dash, and two cup holders and some open storage between the two.  From what I've seen, the center console models usually are equipped with a Bose sound system as well (starting in 2003 I believe).  The extended cab and crew cab models also have decent storage under the rear seat.  There is enough room to keep jumper cables, small tool kit, blanket, flash light, tow strap, snow brush and a few other items.  Like the Tahoe, Yukon, Suburban and other models from this era, the Silverado and Sierra suffer from plastic finish chipping on trim pieces and the stereo and tearing of the seam on the door side of  the driver seat.


The engine, transmission and axles in these trucks are built strong and are very reliable.  The Allison 1000 transmission is considered by many to be the best diesel truck automatic transmission on the market, for many reasons including reliability, electronic braking and other features.  The Allison 1000 was a single overdrive 5 speed transmission from 2001 to 2005 and a dual overdrive 6 speed transmission from 2006 and up.  The axles in these HD trucks are damn near bullet proof and come equipped standard with 3.73 gears or optional 4.10 gears.  The only major issue with the Duramax engine was injector failure on 2001-2004 (early) LB7 engines.  In addition to injector failures, the injectors are difficult to service on the LB7 engines.  The 2004.5 and newer Duramax engines had revised injectors and other changes that made injector service much easier.



This is the first generation Duramax produced from 2001 until early 2004.  Designed by a partnership between General Motors and Isuzu this new Duramax is a 403 cubic inch (6.6L) V-8 turbo charged diesel engine featuring 4 valve per cylinder (32 valve) aluminum heads mounted on a cast-iron block and fed by a high-pressure common-rail (23,000 psi) direct fuel injection system and CP3 injection pump. The LB7 engines only emissions equipment was a diesel oxidation catalyst (catalytic converter).  Power numbers were 235hp @ 2700 and 500ft-lbs @ 1600 rpm from 2001-2003 and in 2004 300hp @ 3100 and 520ft-lbs @ 1800 rpm.



The second generation Duramax was produced from 2004.5 until 2006.  The LLY received a few changes to improve reliability and power over the LB7 engines.  The LLY had an improved valve design that allowed for easier fuel injector access.  This was also the first year of the variable geometry turbocharger for the Duramax line.  This variable geometry design incorporates moveable vanes in the turbo housing which allows the turbo to spool quicker, improving low end response without sacrificing power at higher engine speeds.  The 2006 models had a fuel pressure increase to 26,000 psi and were also the first trucks equipped with the Allison 1000 6-speed automatic transmission.  The LLY was also the first Duramax to be equipped with an EGR valve to circulate exhaust gas back thru the engine for a second burn.  The LLY engines were also equipped with a diesel oxidation catalyst (catalytic converter).  Power numbers were 310hp @ 3000 and 520ft-lbs @ 1600 rpm for the 2004.5 and 2005 engines.  The 2006 engine produced  310hp @ 3000 and 605ft-lbs @ 1600 rpm.



This is the most sought after Duramax engine and was introduced midway into the 2006 model year.  The LBZ received many upgrades including a stronger block design, new piston design, stronger connecting rods, larger fuel rails, improved injector design, improved turbo design, improved intake mouth design and and upgraded 32 bit engine management computer.  Like the LLY, the only emissions equipment was an EGR valve and diesel oxidation catalyst (catalytic converter).  Power numbers for the LBZ were 360hp @ 3200  - 650ft-lbs @ 1600 rpm.



I have owned a few of these Duramax trucks and seen 22-24 mpg highway with them.  The engines make great power, the interior is comfortable and the trucks ride is nice for a heavy duty pick up truck.  If you are in the market for a 3/4 ton or 1 ton truck, I doubt you will be disappointed with a Duramax Silverado or Sierra.






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