FUL5586656 | Genuine Eaton® Transmission Oil Cooler

The fluid stays within its optimal operating temperature
Transmission runs smoother and lasts longer
Improved towing, hauling, and high-performance capability
Lower risk of breakdowns on hills, in traffic, or under load

Most obvious symptom.
You may see a warning light or message like “Transmission Over Temp” on your dash.
Transmission fluid may exceed 200–220°F, which breaks it down quickly.

2. Hard or Slipping Shifts
The transmission doesn’t shift smoothly or slips between gears.
Overheated or degraded fluid from a bad cooler can’t do its job properly.

3. Burnt Transmission Fluid
Fluid smells burnt or appears dark brown/black instead of red or pink.
Caused by excessive heat buildup when the cooler fails.

4. Fluid Leaks
Transmission fluid leaks around the cooler or hoses.
Coolers and their lines can crack or corrode, especially in trucks exposed to road salt or off-road use.

5. Low Transmission Fluid Levels
Caused by slow leaks in the cooler or fittings.
Can lead to starvation of the transmission — especially on inclines or under load.

6. Coolant in Transmission Fluid (or vice versa)
If the cooler is built into the radiator and fails internally, coolant can mix with transmission fluid.
This creates a milky, frothy fluid and can destroy your transmission.

7. Vehicle Goes Into Limp Mode
Some modern vehicles will limit power or RPM if the transmission overheats.
Helps prevent catastrophic damage but is a clear red flag.