How much (up to) weight can I safely pull on the Dam setting? And/or do I need to drop down to the wild or mild setting. Thanks.
Simple question, not so simple answer.
Short answer is up to the CGVWR for your truck.
Long answer is much more complicated.
Heat is your main issue.
To make power you add more fuel, more fuel gives you more heat in the motor and exahust. Monitor this with the EGT gauge on the MM. Try to keep EGT's under 1300 degrees.
Gearing is also a prime concern, too high a gearset ( this includes tall tires) will put an increased load on the driveline w/o adding the trailer weight. Everything has to work harder which equals making more heat, heat is the #1 enemy of your Transmission and torque converter. Beat the fluid up too much and it will burn along with the components of both the Torque Converter and transmission.
How you drive is a big factor, drive like you stole it with 15K behind you and you will not be driving for long without either a major breakdown or a wreck.
The vehicle brakes if overused can warp the rotors in just one hard stop. ( Yes I did this to a 2004 F350 with 14K 5th wheel behind it)
Long story short:
More power doesn't equal more payload. More power does requirea different driving style, adjust accordingly, slow on the power and slow off works real well and do not be in a hurry! Watch the traffic ahead and pedict what is going to happen and what your response will be. Watch EGT like a hawk.
Truck was designed to operate at CGVW safely (Combined Gorss Vehicle Weight Rating) yes you can tow more but adjust accordingly. Add tall tires w/o changing greaing the safety factor declines as well as performance and longevity.
Last tidbit, the turbo is the furthest from the oil pan of any oil passage in the motor, if you have been running hard high egt's and boost, you will need to allow the engine to cool down before shut down, this mean idling for a few minutes (5 or so) to allow the turbo to cool and thus not cooking the oil left inthe bearing passages. If this oil cooks it turns to basicly sand and will kill the bushing/bearing is short order.
Hope this answers your question.