Roughly 36,000 miles. That’s when the average new-car bumper-to-bumper warranty runs out, and it’s where the real math begins. CarMD’s latest Vehicle Health Index puts the average check-engine repair at $554 in 2025, a 33% jump from the year before, largely because the U.S. vehicle fleet just hit an all-time-high average age of 12.8 years. RepairPal’s own cost estimator prices a full transmission replacement at $6,166 to $6,685. Neither number is a coincidence. Automakers engineer components to clear the warranty finish line, not to run forever, and repair-cost data shows exactly which parts tend to give out first once owners are paying out of pocket.

1. Automatic Transmission: $6,166 to $6,685

A full transmission replacement averages $6,166 to $6,685 in parts and labor, according to RepairPal’s cost estimator, enough to total out plenty of older used cars. Failure rates start climbing around 60,000 to 70,000 miles and become genuinely likely once a car crosses the 100,000-mile mark, per longtime mechanical-reference data compiled by aa1car.com. That timeline lines up almost exactly with where a typical 5-year/60,000-mile powertrain warranty runs out, which is exactly why so many owners feel blindsided.

 

2. Water Pump: $885 to $1,134

Water pumps aren’t glamorous, but RepairPal puts the average replacement between $885 and $1,134, split roughly evenly between parts and the labor needed to reach them. The failure curve isn’t gentle. aa1car’s mechanical-reference data shows leak-related failures go up sharply once a pump passes 70,000 miles, and Kelley Blue Book notes older-generation pumps often need replacing somewhere between 60,000 and 100,000 miles. Call it a car payment’s worth of coolant trouble, arriving right on schedule.

3. Timing Chain: $2,109 to $2,751

Unlike a rubber timing belt with a fixed replacement interval, a timing chain is sold as a lifetime part, until it isn’t. RepairPal’s estimator averages a full replacement at $2,109 to $2,751, and on interference engines a chain that stretches or jumps can bend valves and turn a bill into a rebuilt engine. Symptoms typically start as a cold-start rattle well past 100,000 miles, long after the factory warranty has already closed the door on a free fix.

4. Turbocharger: $2,490 to $3,095

Turbocharged four-cylinders are now standard equipment on everything from pickup trucks to compact sedans, and when the turbo itself fails, RepairPal pegs the average repair at $2,490 to $3,095. Turbo specialists estimate the components can spin at six-figure RPMs for up to 150,000 miles with proper maintenance, but that lifespan assumes fresh oil changes and short warm-up periods most commuters skip. Skimp on either habit, and the bill tends to arrive well before that mileage figure does.

5. Catalytic Converter: $1,511

Catalytic converters top CarMD’s list of the most common check-engine repairs, averaging $1,511 apiece, nearly three times the overall $554 average cost of a check-engine fix in CarMD’s 2025 Vehicle Health Index. Federal law only guarantees emissions parts for 8 years or 80,000 miles, and converters tend to clog or fail from age, unburned fuel, or theft-related tampering right around that window. It’s the priciest line item on CarMD’s most-common-repairs chart, and it lands like clockwork once the emissions warranty lapses.

6. Infotainment Screen: $500 to $3,500

Infotainment now ranks as the single most problem-prone system in vehicle ownership, ahead of powertrains and climate control, according to J.D. Power’s 2026 U.S. Vehicle Dependability Study, with glitchy phone-mirroring cited as the biggest driver. That study tracks 3-year-old vehicles, right around where most bumper-to-bumper coverage ends. Replacing a basic touchscreen unit runs $500 to $1,000, while advanced systems with built-in navigation and CarPlay integration climb to $1,500 to $3,500 before installation labor.

7. EV Battery Degradation: Thousands in Fading Range

Electric vehicle batteries don’t die suddenly, but they do fade, losing an average of 2.3% of capacity per year according to fleet-data analysis from Geotab, which works out to roughly 81.6% of original capacity after eight years for heavily used packs. Federal rules require only an 8-year/100,000-mile battery warranty, and once that clock runs out, a full pack replacement can range from about $5,500 for a Nissan Leaf to more than $16,000 for a Chevrolet Bolt, or over $30,000 for some Mustang Mach-E and BMW i3 owners.

None of this is bad luck. It’s amortization. Every warranty term an automaker sets is a calculated bet on exactly when these parts start costing the owner instead of the manufacturer, and the repair-cost data shows that bet pays off with remarkable consistency.