Came with small tires i went up 3/4 ", yes you can manually shift it, It works pretty good until the wind blows then it thinks it needs to live in 2 and 3rd gears.
how was it for towing before you changed your tire size? if it was good you can figure out what ratio to go to, or figure out what rpm and speed your doing and what you would like to change your rpm to for engine torq curve, better to only have to change ratio once to get what you need
tow rating is 6000 # or so i pull a 3000# dry weight trailer, plus 3 people, 2 450 dirt bikes, gear tools, generator and pressure washer. it pulls in over drive no problem until the wind blows then it gets ugly living in 2,3,4 th. i think 3.73 would help it out a lot doesnt help that is the high roof ext model
engine has all kinds of power they are impressive for a gas job.