Mudlite took the words right out of my mouth. Youve got a heating problem you need to address first with the radiator.
Is your radiator clean of debris? Take a water house and back wash the radiator from the engine compartment, or better yet, pull the radiator and back flush the cooling fins being careful to not bend any of them over. Are you running a clutch fan, or flex fan? Stop and go traffic greatly relies on the fan and shroud. Does the shroud only cover half of the blade of the fan? Ive seen shrouds that have the fan completly inside of them, and this causes the air being pulled thru the radiator to stall inside the shroud. Of course if your radiator has internal problems, its got to be fixed, or replaced.
A shroud should cover half of the pitch of the fan. Looking down, you should be able to see half of the fan inside, and half sticking outside of the shroud.
We run our tranny coolers seperate from our radiators to keep the heat from being introduced to the radiator at all. They have their seperate location alltogether.
Hope some of that helps.
Jim