Symptoms
- Noise appears or worsens after 20+ minutes of driving
- Worse in hot weather or after towing
- Noise may fade again after the vehicle cools down and restarts
- Possible burning smell alongside the noise
Likely causes
- CommonFluid thinning excessively when overheatedOverheated fluid loses viscosity and pressure-holding ability, which can cause noise as parts don't get proper lubrication or pressure.
- CommonLow fluid level causing overheatingLow fluid heats up faster and more severely, worsening any heat-related noise.
- PossibleWorn bearing or pump more noticeable at higher heat-expanded clearancesSome wear becomes audible only once components reach operating temperature and clearances change.
- PossibleCooling system or transmission cooler not keeping upAn underperforming cooler lets fluid run hotter than it should, especially in traffic or hot weather.
- PossibleSlipping clutch pack generating heat and noise togetherHeat and slipping-related noise often appear together as a related pair of symptoms.
What to do
- Check the transmission fluid level and condition once the vehicle has cooled; look for a burnt smell or dark color.
- Top off fluid if low and see if the noise improves on a subsequent long drive.
- Note if the noise is accompanied by any warning lights or a burning smell, which would raise the priority.
- Avoid towing or hard driving until this is checked, since heat-related noise often means the cooling capacity is marginal.
- Check that the transmission cooler isn't blocked by debris if visible from under the front of the car.
- Have a shop check fluid condition and cooler function if noise continues after topping off fluid.
- Treat a burning smell alongside hot-noise as more urgent and get it checked sooner rather than later.
Tools and parts
- Dipstick
- Flashlight
Transmission fluid (correct type for vehicle)Search: “transmission fluid type for [make model year]”
When to call a pro
See a mechanic if noise appears mainly when hot, especially with any burning smell, since it often points to marginal cooling or early slipping.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.