The Diesel Wars
In 2000, the best heavy-duty diesel pickups made about 235 horsepower. Then GM showed up with an Ohio-built Duramax making 300, and within a few years Dodge and Ford were trading torque numbers like punches. These three engines defined the era, and they're still pulling trailers today.
- 1LB7 Duramax 6.6L2001–2004 · 300 hp, 520 lb-ft · Chevy and GMC HD
- 2Ford 6.0L Power Stroke2003–2007 · 325 hp, up to 570 lb-ft · Super Duty
- 3Cummins 5.9L common-rail2003–2007 · up to 325 hp, 610 lb-ft · Dodge Ram HD
The theme: the torque war
Before 2001, Ford's 7.3L Power Stroke made 235 hp and 500 lb-ft, and Dodge's 5.9L Cummins made 235 hp and 460 lb-ft. GM had barely been in the conversation. The Duramax changed that overnight, and the next few years turned into an arms race of horsepower and torque ratings, with each brand claiming the crown in turn. Not every engine that came out of it was a winner.
LB7 Duramax 6.6L
2001–2004 Chevy Silverado and GMC Sierra HD
GM didn't have a competitive diesel, so it partnered with Isuzu. Their joint venture, DMAX, built the Duramax in Moraine, Ohio, the same state as our yard. The LB7 arrived for 2001 with Bosch high-pressure common-rail injection, aluminum heads, 300 hp and 520 lb-ft, which instantly beat both Ford and Dodge. Paired with the new Allison 1000 automatic, it was smooth, quiet and strong.
It worked. GM's share of the diesel pickup market jumped from roughly 5% to around 30% in a few years. The LB7 was also the last Duramax without EGR, which is why many owners still prefer it. It was replaced by the LLY in 2004.
Owner's notes: Injectors are the LB7's famous weak spot. A failing injector can push fuel into the oil, so watch for a rising oil level that smells like diesel and smoke at idle. GM's extended injector coverage has long expired, so ask whether they've been replaced. There's no factory lift pump, so check the fuel filter housing for air leaks. On 4x4s, check the transfer case for the known pump-rub wear (see our transmission and transfer case parts), and inspect the front end for worn steering parts.
Watch it
Five red flags on an LB7. Video: Kooshdaakaa Garage on YouTube
A 2001–2007 Duramax buyer's guide. Video: Dirty Diesel Customs on YouTube
Ford 6.0L Power Stroke
2003–2007 Ford Super Duty
Ford answered mid-2003 with a new engine from Navistar. On paper, the 6.0L won the war: 325 hp and 560 lb-ft, rising to 570 lb-ft for 2005, with a variable-geometry turbo and a new five-speed TorqShift automatic. It was more powerful and quieter than the beloved 7.3L it replaced.
In the real world, it became one of the most notorious engines of its era. Problems led to a class-action settlement and expensive court verdicts, and Ford replaced it with the twin-turbo 6.4L for 2008. Fixed properly, though, a 6.0 can be a strong engine, and a whole industry grew up around "bulletproofing" them.
Owner's notes: The stretch-prone head bolts can let head gaskets fail; head studs are the common fix. The oil cooler can clog, which then overheats and ruptures the EGR cooler, so watch for white steam from the exhaust and coolant loss. The FICM sits on top of the engine, where heat and vibration crack its solder joints and cause hard starts; we list tested used FICMs in our modules collection. High-pressure oil system leaks and sticky injectors round out the list. Ask what's been done before buying a truck or an engine.
Watch it
The truth about the 6.0L. Video: Dust Runners Automotive Journal on YouTube
Problem areas to check on a 6.0. Video: Thoroughbred Diesel on YouTube
Cummins 5.9L common-rail
2003–2007 Dodge Ram 2500 and 3500
Dodge struck back fast. For 2003, the Cummins inline-six switched to Bosch common-rail injection, jumping to 305 hp and 555 lb-ft in high-output form while running about 10 decibels quieter than before. In mid-2004, Dodge pushed it to 325 hp and 600 lb-ft and put a "600" badge on the truck so everyone knew. For 2005 the rating climbed again to 610 lb-ft, the highest of the three.
Dodge kept improving the trucks around it, adding the G56 six-speed manual for 2005 and the Mega Cab for 2006. Most Ram HD buyers in this era chose the Cummins. The 5.9 was replaced by the 6.7L in 2007 as emissions rules tightened.
Owner's notes: Injectors typically last a long time but hate contaminated fuel, and the 2003–04 and 2004.5–07 injectors are not interchangeable. Lift pump failures are common, and a failed pump can damage the injection pump, so keep the fuel system healthy. Replace injector connector tubes whenever injectors come out. Accelerator pedal sensor faults ("dead pedal") show up on some trucks. For drivetrain work, we pull axles and differentials with gear ratios listed, plus transfer cases.
Watch it
What to check on a 2003–07 Cummins. Video: Thoroughbred Diesel on YouTube
Top third-gen Cummins issues. Video: Just Diesels on YouTube
By the numbers: peak torque in the war years
Highest factory torque rating each engine reached during 2001–2007.
Where the diesel wars went next
New emissions rules in 2007 forced all three makers to add diesel particulate filters, and the numbers kept climbing: the LMM Duramax, the 6.7L Cummins and Ford's twin-turbo 6.4L all arrived rated around 350–365 hp and 650–660 lb-ft. The torque war never really ended. But the trucks from 2001–2007 are now the sweet spot for people who want a diesel without modern emissions complexity, and you'll find diesel dropouts in Engine Swaps as they come in.
Diesel truck parts at J&J
We pull axles, transfer cases, modules and engine parts from real HD donor trucks. Browse Engine Swaps, axles and differentials, Chevy, Ford and Dodge and Ram parts.