Data story
What Breaks When You Tow? 358 Diesel Owners Who Were Pulling a Trailer
Published · 5 min read
"Pulling a horse trailer engine just completely stalled without warning. I lost all steering and brakes."
Owner of a 2002 F-250 7.3, on a remote highway at night, 2019. NHTSA complaint 11271348
Most diesel pickups are bought to tow, and a failure with 10,000 pounds behind you is a different event from the same failure on an empty truck. So we pulled out the owner complaints that mention towing and compared them with all the rest.
Of 4,433 complaints on ten Power Stroke, Cummins and Duramax engine families, 358 describe the truck towing or pulling a trailer, camper, boat or load. They read differently.
What happened, towing vs not towing
- Overheating (towing)6%
- all other complaints2%
- Brakes or exhaust brake (towing)32%
- all other complaints14%
- Lost power or went into limp mode (towing)26%
- all other complaints13%
- Steering (towing)21%
- all other complaints13%
- Transmission (towing)14%
- all other complaints9%
- Engine stalled or shut off (towing)24%
- all other complaints19%
Complaints that mention towing Every other complaint
358 towing complaints and 4,075 others, from 4,433 unique NHTSA complaints on ten diesel engine families (Power Stroke 7.3 to 6.7, Cummins 5.9 and 6.7, Duramax LB7 to L5P), pulled 2026-09-07 to 2026-10-16. Keyword matches, samples read by hand. A complaint can describe several outcomes.
Heat and power are the towing problems. Overheating, power loss and limp mode all show up two to three times as often when there is a trailer behind the truck. That makes sense: towing is the hardest sustained work these engines do, and it finds the weak cooling system, the leaking boost hose and the tired turbo that an empty truck hides.
Steering and brakes come up because of stalls. When we read the towing complaints that mention brakes or steering, most describe the same chain: the engine stalls, power steering and brake assist go with it, and the driver is wrestling a heavy truck and trailer to the shoulder. The steering and brakes still work, but they take far more force than you expect.
"Pulling a loaded 5 horse trailer when the truck would not accelerate, 15 seconds later engine cut off."
Owner of a 2003 F-350 6.0, at 70 mph in the left lane, 2009. NHTSA complaint 10284128
Which system it is about
- Fuel system (towing)23%
- all other complaints26%
- Turbo / boost (towing)11%
- all other complaints6%
- Stall or power loss, no part named (towing)8%
- all other complaints7%
- Cooling / head gasket / oil cooler (towing)7%
- all other complaints3%
- Sensors and electronics (towing)7%
- all other complaints5%
- DPF / regeneration (towing)4%
- all other complaints3%
- Engine internals (towing)4%
- all other complaints2%
- DEF / SCR (towing)3%
- all other complaints6%
- EGR (towing)3%
- all other complaints3%
Complaints that mention towing Every other complaint
358 towing complaints and 4,075 others, from 4,433 unique NHTSA complaints on ten diesel engine families (Power Stroke 7.3 to 6.7, Cummins 5.9 and 6.7, Duramax LB7 to L5P), pulled 2026-09-07 to 2026-10-16. Keyword matches, samples read by hand. A complaint can describe several outcomes.
The fuel system leads in both groups, so towing does not change what fails most. What it changes is the order behind it: turbo and boost problems and cooling problems (radiators, oil coolers, head gaskets) take a larger share when the owner was towing. DEF problems take a smaller one.
"This truck is rated to tow 16,000 + pounds and I'm towing around 15,500 and it can't do it without overheating the coolant and transmission."
Owner of a 2005 GMC Sierra Duramax, 2005. NHTSA complaint 10136982
Which engines draw the most towing complaints
| Engine | Engine complaints | Mention towing | Share |
|---|---|---|---|
| 7.3 Power Stroke 1994.5-2003 | 607 | 49 | 8% |
| 6.0 Power Stroke 2003-2007 | 980 | 66 | 7% |
| 6.4 Power Stroke 2008-2010 | 159 | 17 | 11% |
| 6.7 Power Stroke 2011-2026 | 666 | 48 | 7% |
| 5.9 Cummins 1994-2007 | 477 | 21 | 4% |
| 6.7 Cummins 2007.5-2018 | 656 | 50 | 8% |
| 6.7 Cummins 2019-2025 | 318 | 33 | 10% |
| Duramax LB7-LMM 2001-2010 | 283 | 32 | 11% |
| Duramax LML 2011-2016 | 212 | 30 | 14% |
| Duramax L5P 2017-2026 | 185 | 18 | 10% |
Same complaint sets as our engine comparison; a complaint filed under two engines counts for both here.
The share is highest on the Duramax LML and the older Duramax trucks and lowest on the 5.9 Cummins. That is a statement about what owners wrote, not about which truck tows best: owners who tow heavy may simply buy some trucks more than others.
What to do before a long tow
- Watch the temperatures, not only the warning lights. A gauge or scan tool that shows coolant and transmission temperature lets you slow down before a warning, especially on long grades.
- Check the boost side. A loose or cracked charge air hose gives low power under load and sets low-boost codes. Our P0299 guide shows where to look on the 6.7 Power Stroke.
- Fix the fuel system first. Fuel problems lead every list. A pump or lift pump that is marginal on an empty truck can quit with a trailer on. See the CP4 pump guide and the VP44 guide.
- Know what a stall feels like. If the engine quits, the truck will still steer and brake, with much more effort. Hold the wheel firmly, brake steadily and get to the shoulder.
- Run the VIN. Some of the failures in these complaints, such as CP4 pumps on 2019-2020 Rams, are covered by recalls on certain trucks. Our VIN lookup lists them.
What we cannot tell you
- Whether towing causes the failure. Some owners mention towing because that is how they use the truck, not because it was towing at that moment. We kept those in.
- Failure rates. These are complaints, not a measure of how many trucks fail when towing.
- Gas trucks. This story covers diesel engines only.
FAQ
Why does my diesel overheat when towing?
Towing is the heaviest sustained load these engines see. In owner complaints, overheating is three times as common when the truck was towing. Radiators, fans, oil coolers and coolant condition are the usual suspects, so check those before a long tow in hot weather.
Why does my diesel lose power when towing uphill?
Owners describe boost leaks, turbo and actuator faults, fuel delivery problems and limp mode triggered by high temperatures. Power loss and limp mode are twice as common in towing complaints as in the rest.
What happens if a diesel stalls while towing?
Power steering and brake assist are lost with the engine. The truck can still be steered and stopped, but it takes much more force. Many owners in our sample describe this, so practice the idea before you need it.
Which diesel truck is best for towing?
Owner complaints cannot rank them. The share of complaints that mention towing is highest on the Duramax and lowest on the 5.9 Cummins, but that reflects how owners use the trucks as much as how they hold up.
Go deeper
- Power Stroke vs Cummins vs Duramax: what owners report
- Power loss, engine by engine · Overheating, engine by engine · Stalls
- Diesel or gas Super Duty · Recalls by engine
Sources. NHTSA owner complaints database (US government public domain), the complaint sets of our ten diesel engine articles, pulled 2026-09-07 to 2026-10-16. Towing complaints matched on phrases such as "while towing", "pulling a trailer", "fifth wheel" and "gooseneck", with "had it towed" and "semi trailer" left out; samples read by hand on 2026-10-31. Owner quotes normalized for capitalization; complaint numbers given so you can read them in full. Torque Index takes no paid placement.