Boiling point: How much can your diesel auto trans handle?

On my 2005 Ford 3/4T 4X4 diesel, I don't know how much pain it can take because I haven't been able to find that point so far. When I was going to start hauling a heavy trailer I went to my local Ford specialty diesel truck shop and they said don't worry about it, the Ford has a good cooler and transmission.

Two years later after hauling heavy loads (some of them actually overloaded on hills), I haven't been able to make the transmission temp hardly budge and it's working fine.

Bill

Bill