Symptoms
- Whine present with the car in neutral or park, engine running
- Whine changes pitch with engine RPM rather than road speed
- Noise may lessen briefly right after a fluid top-off
- Possible vibration accompanying the whine
Likely causes
- CommonLow transmission fluidLow fluid can cause the pump to draw in air (cavitation), producing a whine.
- CommonWorn transmission pumpThe pump that builds hydraulic pressure runs whenever the engine runs, so pump wear whines even in neutral.
- PossibleWorn input shaft bearingA bearing supporting the input shaft can whine independent of which gear is selected.
- PossiblePower steering pump noise (often mistaken for transmission)A failing power steering pump nearby can sound similar and is worth ruling out.
- PossibleAccessory belt or pulley noiseA worn belt or pulley bearing elsewhere in the engine bay can be mistaken for transmission whine.
What to do
- Check the transmission fluid level and top off if low, then see if the noise changes.
- Turn the steering wheel while parked to see if the noise changes, which would point to power steering rather than the transmission.
- Listen with the hood open (carefully, away from moving parts) to help localize the sound to the front, side, or underneath.
- Note if the pitch changes with engine RPM (suggesting the pump or an accessory) versus road speed (suggesting gears).
- Avoid revving the engine excessively while diagnosing to prevent added stress if something is failing.
- Have a mechanic use a mechanic's stethoscope or similar tool to pinpoint the exact source if it's not obvious.
- Address low fluid or a confirmed pump/bearing issue promptly, since pump failure can lead to loss of shifting ability.
Tools and parts
- Flashlight
Transmission fluid (correct type for vehicle)Search: “transmission fluid type for [make model year]”
When to call a pro
See a mechanic if fluid is fine and the whine continues, especially if you can't rule out power steering, since pinpointing the source usually needs a lift and stethoscope.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.