The Lemon Index
The 6.6 L V8 turbo diesel in the Chevrolet Silverado 2500HD/3500HD and GMC Sierra 2500HD/3500HD, model years 2001–2004. Owners filed 592 complaints about trucks with it (matched by VIN); 7% name the engine, #10 of the 12 diesel truck engine generations we track (1 = the most).
Known issues, checked against owner complaints
Problems owners of trucks with this engine name much more often than owners of other diesel truck generations (at least 1.5× the median, and 10+ complaints):
- Injectors. 72 of 592 owner complaints (12%) mention an injector, against a median of 1.2% for the other diesel truck generations we track.
Fuel is dumping into injectors. 2001 gmc sierra 2500 diesel. only has 135,000 miles!! engine boggs down when climbing hill, bridge, or towing.
2001 owner · NHTSA complaint 11389800
What YouTube owners say Tone 0-100, higher = more praise than trouble.
Average owner tone 39/100 across 4 model years, from 182 videos about this engine and its cars.
Most-watched videos
- REVIEW: Everything Wrong With A 6.6 Duramax LB7 649,437 views
- Duramax LB7, LLY, LBZ, LMM, LML, L5P Explained! 378,938 views
- How to Install Duramax LB7 Injectors 337,218 views
Counted from video titles and captions: praise words against trouble words, weighted by views. Videos only count when the title names this engine or a car that had only this engine in those years.
Owner complaints by model year
Counts of complaints filed so far. Older trucks have had longer to collect them, and popular years draw more because more were sold: no one reports sales by engine, so there's no per-truck rate. Compare the shares below instead.
What owners complain about
Share of this engine's complaints that name each area (one complaint can name several).
What owners write
| Complaints that | Count | Share | Median, other diesel truck engines |
|---|---|---|---|
| Mention an injector | 72 | 12% | 1.2% |
| Say the engine stalled, shut off or lost power | 32 | 5.4% | 7.8% |
| Mention a fuel leak | 16 | 2.7% | 0.4% |
| Mention an oil leak | 5 | 0.8% | 0.5% |
Counted from the owner's own words in each complaint (all of the truck, not only the engine). A share, not a failure rate.
When problems show up
Half of the owners who gave a mileage reported the problem between 56,760 and 127,000 miles; the middle report was at 90,000 miles (527 complaints with a mileage).
Recalls that name this engine 1
01V220000 Jun 2001 Interior Lighting
Vehicle description: certain pickup trucks equipped with 6.6l diesel engines fail to comply with requirements of fmvss no. 105, "hydraulic and electric brake systems." these vehicles have a brake system warning light in the instrument cluster that may not illuminate when the brake fluid is low. In addition, when the brake fluid is low, the vehicle may not meet the partial system requirements of fmvss no. 105.
Fix. Dealers will change the location of a wire connection in the underhood bussed electrical center. Owner notification began july 9, 2001. Owners who take their vehicles to an authorized dealer on an agreed upon service date and do not receive the free remedy within a reasonable time should contact chevrolet at 1-800-222-1020 or gmc at 1-800-462-8782.
NHTSA recalls on these trucks and years whose text names this engine (its size, or diesel / Cummins / Duramax / Power Stroke). The rest (brakes, air bags, wiring ...) are on each truck year's page.
Trucks with this engine
In owners' words
Right/ rear firestone steel-tex tire , size: lt245/75r16, dot: vn11v1c4800 is starting to show signs of deformation in sidewall. tire is original equipment , and has approximately 7,000 miles on it. deformation is approximately 2 to 3 inches in length. *jg
2001 Chevrolet Silverado 2500HD/3500HD and GMC Sierra 2500HD/3500HD owner · NHTSA complaint 898202
While traveling at 40 mph another vehicle ran a light and consumer's vehicle hit other vehicle. upon impact, none of the frontal airbags deployed. *ak nlm
2001 Chevrolet Silverado 2500HD/3500HD and GMC Sierra 2500HD/3500HD owner · NHTSA complaint 896246
After changing tires abs system would not work properly on wet roads. dealer was told not to reset abs system.
2001 Chevrolet Silverado 2500HD/3500HD and GMC Sierra 2500HD/3500HD owner · NHTSA complaint 881246
Against the other diesel truck engine generations
| Engine | Years | Complaints | Name the engine | Name the fuel system | Stalled or lost power | Recalls naming it |
|---|---|---|---|---|---|---|
| 6.0 Power Stroke | 2003–07 | 1,708 | 34% | 16% | 31% | 2 |
| 6.4 Power Stroke | 2008–10 | 572 | 28% | 7% | 11% | 2 |
| Duramax L5P | 2017–26 | 1,229 | 16% | 10% | 14% | 2 |
| 7.3 Power Stroke | 1999–03 | 2,049 | 15% | 5% | 12% | 1 |
| Duramax LML | 2011–16 | 779 | 13% | 20% | 17% | 0 |
| 6.7 Cummins | 2007–26 | 7,667 | 11% | 8% | 6.4% | 9 |
| 6.7 Power Stroke | 2011–26 | 5,640 | 10% | 11% | 7.8% | 6 |
| Duramax LBZ | 2006–07 | 186 | 8% | 5% | 7.0% | 0 |
| Duramax LMM | 2007–10 | 385 | 8% | 6% | 5.2% | 0 |
| Duramax LB7 | 2001–04 | 592 | 7% | 17% | 5.4% | 1 |
| Duramax LLY | 2004–06 | 374 | 7% | 11% | 7.8% | 0 |
| 5.9 Cummins | 1999–07 | 3,245 | 4% | 7% | 5.0% | 0 |
Shares of each engine's own complaints, matched by VIN. They show what owners complain about, not how often trucks break. Every diesel truck engine compared
Quick answers
Is the Duramax LB7 reliable?
No one reports sales by engine, so there's no per-truck score. Of the 592 complaints owners filed about trucks with it, 7% name the engine, #10 of 12 diesel truck engine generations we track (1 = the most). 72 (12%) mention an injector, against 1.2% for its peers.
What trucks have the Duramax LB7?
In our data: the Chevrolet Silverado 2500HD/3500HD and GMC Sierra 2500HD/3500HD, model years 2001–2004, matched by the VIN in each owner complaint.
What are the most common Duramax LB7 problems?
In owner complaints to the government: brakes, fuel system, electrical.
How many recalls name the Duramax LB7?
1 NHTSA recall on these trucks names it.
Source: NHTSA owner complaints (FLAT_CMPL + COMPLAINTS_RECEIVED_2025-2026), received through 20261109; engines: NHTSA vPIC VIN decoder; NHTSA recalls API. Engine names and years: GM (RPO codes).