Known engine & transmission defects
Some powertrains earn a reputation. These are the engines and transmissions with a documented one — class actions, federal investigations, and owner complaints by the thousands — ranked, named, and linked to the full record.
When a specific engine or transmission is bad, it’s usually bad across every car it went into — which is exactly why knowing the unit matters more than knowing the badge. The same problem transmission shows up under three different nameplates. This is the reference for the ones with a paper trail: what the defect is, how loud the complaint record is, and where to read the detail.
The defect record, ranked
By total NHTSA complaints across every vehicle that used the unit.
Browse the full hubs: all engine families · all transmission families.
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Common questions
What makes an engine or transmission a "known defect"?
Inclusion here requires a documented, widespread pattern — a class action, an NHTSA investigation, a manufacturer service bulletin, or a large volume of owner complaints across the affected fleet — not a one-off. These are the units with a track record, shared across multiple models and years.
What is the most-complained-about engine or transmission?
By total NHTSA complaints across every vehicle that used it, the Ford 6F35 leads this list with 52,412 complaints. The full ranking is above, each linking to the family’s full record and the vehicles affected.
How are the complaint totals counted?
Each family maps to the specific year/make/model vehicles that used the unit. We sum NHTSA complaints, recalls, and harm allegations across every one of those vehicles, so the total reflects the whole fleet that shared the engine or transmission — not a single model.
Does a defective family mean every car with it is bad?
No. A documented family-level defect raises the odds, but build year, maintenance, and the specific failure all matter. Use the family page to see which model years and which symptoms dominate, then check the individual vehicle.