You can't over work your engine or transmission. Worst case, if you're severely overloaded, a larger transmission cooler may be useful, but you won't hurt anything.
Keep in mind the V10 with the 6-speed TorqueShift is used in Medium Duty Trucks up to 37,000 gross combined.
I regularly run at 22,000 combined, sometimes as high as 25,000 combined, and I have over 450,000 miles and engine and transmission are original, except for some PM items (coils, injectors, timing chain, radiator) and my transmission is the old 4R100, which is not near as capable as the 6R140 that you have.
