Transmission fluid in the coolant............

I'm sure that at somepoint in history (and I'm not just talking 6.0 here) there has been such, but I've never seen or heard of it. Maybe someone else will chime in here.

Engine oil cooler failure is, unfortunately, all too common on these engines.

Used car salesmen trying to sell POS is, unfortunately, all too common on this planet.

Make him an EXTREME lowball offer on this truck OR ask for a warranty that HE pays for that covers EVERYTHING. Good luck.

I'm not trying to be a total pessimist here but I am trying to keep you from making an expensive mistake. Radiator replacement is CHEAP (and tells me they don't know anything about this truck). If you have tranny fluid in the radiator how is the tranny would be my next question. You could probably smell Mercon SP in the degas bottle cause it literally smells like poo.