is your engine getting hot also?
Remember, the cooling of your transmission is only as good as the cooling system for your engine as the fluid passes through the bottom of the radiator. If the coolant is hot it wont effectively cool the transmission fluid. Also when is the last time it was serviced? The filter may be partially blocked and its a good idea to service the 4 speeder regularly anyway.
Has it just started to happen? as a little heat is normal but it should not be excessive.
Lets go find that Hotdog tree I planted
Lowered EF Futura
Black Steelies ( too cheap to buy proper mags )