Symptoms
- Engine RPM rises but acceleration lags behind
- A 'rubber-band' or delayed feel between shifts
- Whining or humming under load
- Burning smell from under the hood
Likely causes
- CommonLow or degraded transmission fluidFluid carries the hydraulic pressure and lubrication that keep clutch packs from slipping.
- CommonWorn clutch disc (manual)A thin or glazed disc can't grip fully under load.
- CommonWorn internal clutch packs (automatic)High mileage wears the friction material that locks gears together.
- PossibleFaulty torque converterA converter that won't lock up properly can feel like slipping.
- PossibleWrong or contaminated fluidThe wrong fluid type, or water or coolant contamination, changes how well it grips.
What to do
- Check the transmission fluid level and smell it; a burnt odor or dark color points to wear or overheating.
- Top off fluid if low, using the exact type the manufacturer specifies.
- Note when slipping happens: at low speed, high speed, or only under hard acceleration.
- On a manual, check clutch pedal free play, especially if slipping started right after a clutch job.
- Avoid towing, hauling, or hard acceleration until it's diagnosed, since slipping generates heat that speeds up damage.
- Have the fluid and filter serviced if it's overdue, then retest.
- If slipping continues after a fluid service, get a diagnostic scan for transmission trouble codes.
Tools and parts
- Dipstick (if equipped)
- OBD-II scanner (optional)
Transmission fluid (correct type for vehicle)Search: “transmission fluid type for [make model year]”
When to call a pro
See a transmission shop promptly; slipping that persists after a fluid check usually means internal wear, and continuing to drive on it can turn a repair into a full rebuild or replacement.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.