Is there more to a F350 drive train than an F250 than the extra leaf in the rear spring package?
Note sure, but I researched it and from what I can tell the F250 with the towing package comes with a heavier differential that has a larger ring gear than the truck without the package. That was not from the Ford Web site. Can't remember where I read that.
No difference in the rear differential in super dutys until you get to dual rear wheels. Duallys do have a different rear end. On single wheel 250's and 350's no difference except leaf springs.
From what I've read, the regular F250 has a Sterling rear differential with something like a 10.5" ring gear. F250 with towing package or SRW F350 has a Dana M275 with a 10.8" ring gear. Double check my information because I'm no expert and this info is from the Internet, but multiple sources report the same thing.
I just google and here's one such thread. Not sure what year models this applies to.
https://www.ford-trucks.com/forums/1454071-new-dana-axles-2.html
