Engine or transmission? Which one owners of each car complain about

A bad drivetrain record can mean a bad engine or a bad transmission, and the checks differ. Which it is for 303 problem model years, from NHTSA data.

By Eyal Malka · November 5, 2026 · Data: NHTSA, updated October 3, 2026 · How we score

When a used car has a bad drivetrain record, the first useful question is: which part? A model year where owners complain about the engine needs different checks, different questions and a different test drive from one where they complain about the transmission. The difference also changes what a problem costs to live with and what a seller's "it's been fixed" actually means.

NHTSA's complaint records answer the question directly, because every complaint is filed under one or more component categories. This guide splits the problem model years we track into engine-led and transmission-led, lists the clearest of each, and shows why the answer can flip between two years of the same car.

How NHTSA files a complaint

Each owner complaint carries one or more component tags. Three of them make up what this site calls the drivetrain:

• Engine (sometimes "Engine and Engine Cooling"): the engine itself, its cooling, oil and timing systems.
• Power Train: the transmission, whether automatic, manual, CVT or dual-clutch, plus the driveline, axles and transfer case.
• Fuel/Propulsion System: the fuel pump, injectors and lines, and on hybrids the propulsion system.

A complaint can carry more than one tag: an owner whose car stalled and then would not shift may be filed under both Engine and Power Train. The drivetrain share on every page of this site counts a complaint once if it carries any of the three. How to read these numbers.

For this guide we looked at the two largest categories separately, as a percentage of all of a model year's complaints. Our cached breakdown keeps the eight largest categories for each model year, so a category too small to make that list counts as zero here. That only matters at the low end; for the model years below, the leading category is always in the list. The figures come from tools/guide-stats.mjs.

The split across problem model years

We took every model year with at least 300 complaints, which is 514 of them. Of those, 303 have a drivetrain share of 40% or more, the level we score as high. In 192 of the 303 the Engine category is larger than Power Train. In 111 Power Train is larger.

So among cars with a bad drivetrain record, engine-led problems outnumber transmission-led ones by about five to three. That is worth knowing because the popular advice runs the other way: most used-car guides talk about transmissions, and most buyers test-drive for a slipping gearbox. The more common problem in this data is the engine.

Model years where the engine leads

These are the model years where Engine complaints make up the largest share of all complaints, among high-scoring years with 300 or more complaints:

In each of these, between 73% and 90% of all complaints are drivetrain complaints, and the Engine category alone accounts for between 62% and 84% of everything owners filed. Hyundai and Kia have nine of the twelve places, spread across four nameplates, the Kia Sportage, Kia Soul, Hyundai Santa Fe and Hyundai Sonata, rather than one model. The other three are the 2018 Ford Escape and the 2022 and 2023 GMC Yukon.

The Hyundai Sonata shows how long an engine pattern can last: the Engine category is between 36% and 62% of all complaints in every model year from 2012 to 2019, while Power Train never reaches 13% in any of them.

Model years where the transmission leads

And these are the model years where Power Train complaints make up the largest share:

In these, Power Train alone is between 55% and 66% of all complaints. The Ford Focus and Fiesta are here with their dual-clutch years, along with the Ford Edge, Ford Expedition, Toyota C-HR and Fiat 500, and the Jeep Cherokee, whose Power Train category is between 43% and 58% of all complaints in every model year from 2014 to 2021. These are cars where a careful test drive can tell you a good deal, because transmission faults tend to show up as something you can feel.

The same car can change sides

The answer is a property of the model year, not the nameplate. Three examples from the data:

• Nissan Rogue. From 2010 to 2013 Power Train is between 43% and 52% of all complaints and Engine between 12% and 17%: a transmission story. In 2022 that reverses, with Engine at 51% and Power Train at 14%. A buyer who has read that "the Rogue's problem is the CVT" would be checking the wrong thing on a 2022.
• Ford Escape. The 2017 to 2019 Escape score between 84% and 90%, and Engine is the larger category every year (53% to 64% of all complaints against 15% to 21% for Power Train). The 2020 drops to 26%.
• Honda Accord. In 2018 and 2019 the Accord's drivetrain share rises to 44% and 42%; Engine and Fuel/Propulsion carry it, while Power Train is too small to make the top eight categories. Those are the years the turbocharged engines arrived; the turbo engine guide has that side of it.

Why it matters which one it is

The checks are different. A transmission problem usually shows itself on a test drive: a shudder, a slip, a delay into gear, a flare of revs. The transmission check guide is the script. An engine problem often does not show on a twenty-minute drive at all. Oil consumption, coolant loss and some bearing failures develop over thousands of miles. For an engine-led model year, the paperwork and the inspection matter more than the drive: oil-change records, the oil level and condition on the dipstick, the coolant level, stored fault codes, and a mechanic's look at the car. The oil consumption guide covers one of the commonest engine complaints in detail.

The question for the seller is different. For a transmission, ask whether it has been serviced, reprogrammed or replaced. For an engine, ask how often it needs oil between changes, whether the engine has been replaced or repaired, and whether any warranty extension or recall work was done. Our guide to questions to ask a seller about the transmission covers the first set.

"It's been fixed" means different things. A replaced transmission from the dealer, with the updated part, can genuinely end the story. An engine repaired under a program for a known defect may or may not have been replaced with an improved design. Ask what was done, and get the paperwork.

Recalls do not settle it. In our data, 31% of the model years with the most concentrated drivetrain complaints have no recall on a drivetrain component at all. How to check a VIN for open recalls explains what a recall check does and does not cover.

How to find out for the car you are looking at

1. Check the VIN. The free report shows the model year's drivetrain share and its complaint breakdown by component, so you can see whether Engine or Power Train leads.
2. Open the model-year page for the component chart and the years either side. Every car in the tables above links to one.
3. Plan the inspection around the answer. Engine-led: records, fluids, codes, a mechanic. Transmission-led: a cold-start test drive with stop-and-go traffic, then a mechanic.

Frequently asked questions

Are engine problems or transmission problems more common in used cars?

In NHTSA owner-complaint data, engine-led problems are more common. Of 303 model years we track with at least 300 complaints and a high drivetrain share, the Engine category leads in 192 and Power Train leads in 111.

What does "Power Train" mean in an NHTSA complaint?

It is NHTSA's component category for the transmission and driveline: automatic, manual, CVT and dual-clutch transmissions, axles, driveshafts and transfer cases. Engine faults are filed under Engine, and fuel-delivery faults under Fuel/Propulsion System.

Can a test drive find an engine problem?

Sometimes, but less reliably than a transmission problem. Faults like oil consumption or slow coolant loss develop over thousands of miles and may not show on a short drive. For a model year where engine complaints lead, service records and a mechanic's inspection matter more.