My gearbox has hunting issues when it heats up.
The tranny fluid runs through the radiator, then through the cooler, but it's still sending too much heat into the gearbox.
The surface area on the cooler just isn't big enough.
It's OK on long trips when I'm not changing gears constantly and it's getting a good constant flow of cool fresh air, but for city driving, with the constant stop start and gearchanging, it just can't deal with it.