Could the contradiation in my posts be on account of statements I made that were intended to be understood as sarcastic?
Yes we agree that with deeper gears more weight can be towed.
The weight of the hypothetical trailer I used in the example of a 3.55 srw towing against a f450 was a 15000 lb trailer.
I am trying to point out that for lighter RVs such as a 15000 lb RV there is no advantage to deeper rear gears.
The theoretical story of the f350 srw being able to slightly out pull a f450 from 40 mph all the way to 70 mph with a 15000 lb rv in tow on any grade from level to 7% serves to demonstrate that fact.