My lowly entry-level Ram 2500 w/5.7 Hemi, 3.73 gears, and 5 speed tranny had no problem towing our loaded 8,250 lb. TT (TV & TT = 15,000 GCVW) throughout the Smoky Mts. last summer. My engine/tranny temps barely increased after spending hours in the mountains in 80 degree temps...
For a number of years I towed loaded construction trailers, flatbeds, etc. behind a variety of 1/2, 3/4, & 1 ton trucks. IMO my Ram 2500 could handle 17,000 GCVW more safely than the F150 EB that is rated @ 17,000 even though my sticker is only 15,000... I think marketing departments play with the GCVW, payload, etc. numbers depending on what else they have rolling off the line at the time & what other manufacturers are doing.
For example, regarding the lesser Ram 1500, PickupTruck.com noted in 2009,
Ram's maximum towing capacity has been bumped from 9,100 pounds to 10,450 without any apparent hardware changes.
Later, in 2012, the only change for the stock 2500 was a slightly improved torque converter and a change in the electronic shift sequence so their 5 speed tranny uses gears 2 & 3 in succession vs. choosing one or the other based on acceleration & load. Because of this, it is now referred to as a 6-speed even though it uses the same parts w/different shift pattern...
Although Ram's stock trannies are not the best in the market, I'm sure my tranny is capable of handling a GCVW of 17,000. So far I've always hit the CAT scales at just below GCVW but should we go slightly over, I still feel safe... In comparison, I have towed with 1/2 ton trucks well under GCVW & did NOT feel safe. The soft rear-end felt very squirrely to me & I was glad to snag a 3/4 or 1 ton from the boss the next time I needed to haul the same load...