School me on replacing gears...

[Chrispbrown36]

The tires that are on there are 31x10.5-15's and are brand new so they should be around for a while. I don't have any plans to lift it or go too big on the tires (mostly due to price), so I will probably stay with the size I have. As far as pulling goes, the biggest thing (other than my rear end) I tow is a 16 ft jon boat, so I don't need a ton of power. I would like some more umph taking off though. Honestly at this point I am not sure at this point if it is the gears or the engine that are doggy. The motor seems to be the only thing that wasn't really well maintained on the truck and I am just beginning to pick through the oil leaks to see what is going on under the hood.