An automatic transmission selects gears for you using hydraulics, electronics and a set of internal clutches and bands. When something goes wrong you may notice odd shifting, noises, smells or warning lights. This article covers common problems, their causes and what repairs may cost. Costs and lifespans vary widely by vehicle, so treat anything here as rough orientation only.
Common Warning Signs
- Slipping gears: Engine revs rise without the car accelerating as expected, or the car seems to change gear on its own.
- Delayed or harsh shifts: A pause before the car moves after selecting Drive or Reverse, or a hard clunk into gear.
- Shaking or shuddering: Particularly when shifting or at steady speeds. See also why a car shakes.
- Whining, humming or clunking: Sometimes more noticeable in neutral.
- Burning smell: Can indicate overheated transmission fluid.
- Fluid leaks: Transmission fluid is often reddish, though color varies.
- Check engine or transmission warning light: Stored codes can help locate faults. Our dashboard warning lights guide explains the common symbols.
- Car will not move in gear: Needs prompt professional attention.
What Is the Most Common Failure?
There is no single answer, but problems tied to fluid are among the most frequently cited: low, leaking, old or overheated fluid. Others include worn clutch packs, a failing torque converter, faulty solenoids or sensors, and valve body problems. See automatic transmission clutch problems for more on the internal clutches.
Common Causes
Low or Degraded Fluid
Fluid lubricates, cools and provides hydraulic pressure. Leaks from seals, pans or lines, or fluid that is old and burnt, can cause slipping and overheating. Some modern transmissions have no dipstick, so check the owner’s manual or have a shop inspect it.
Worn Internal Parts
Clutch packs, bands and seals wear with mileage and hard use.
Torque Converter Faults
A failing torque converter can cause shuddering, slipping or overheating.
Electronic and Solenoid Faults
Sensors, solenoids or the control module can cause erratic shifting, sometimes fixable without opening the transmission.
Overheating
Towing, heavy loads and stop-and-go driving raise transmission temperature. Heat is a major cause of wear.
What to Do If You Suspect a Problem
- Note the symptoms and when they occur
- Check for leaks under the car and look at the fluid if your car has a dipstick
- Have codes read (see reading check engine codes)
- Get a transmission-focused inspection early; small repairs are usually less costly than rebuilds
- Avoid towing or hard driving until it is checked
Repair and Replacement Costs
Costs depend on make, model, labor rates and the problem. As broad orientation:
- Fluid service or a minor leak repair is usually at the lower end.
- Solenoid, sensor or valve body work is typically a mid-range repair.
- A rebuild or replacement is commonly several thousand dollars, and for some vehicles can exceed that.
Ask for written quotes, ask what the diagnosis is based on, and consider a second opinion before agreeing to a rebuild. For an older vehicle, compare the cost with the car’s value.
How Long Does an Automatic Transmission Last?
Many are expected to last well over 100,000 miles with proper care, and some much longer, but results vary by design, use and maintenance. Following the fluid service schedule in your manual, avoiding overheating and addressing leaks early all help. Some manufacturers call fluid “lifetime”, but many mechanics still recommend periodic service, so check with a trusted shop.
Which Cars Have the Worst Transmission Problems?
It is hard to answer fairly. Reliability differs by model year and transmission type, and manufacturers revise designs. Check recall and technical service bulletin information and owner reports for the exact model and year you are considering.
Related Reading
For other engine and drivetrain symptoms, see our engine troubleshooting guide.