If you get on a 10-speed bike, put it in the tallest gear and try to pedal forward from a stop, you will find it quite difficult to do or at least until you get going. Drop it down to the smallest gear and you'll find it to be a lot easier. This is called gear reduction and there's a reason why your ring and pinion comes in a ratio like 3.73 to 1. That is, your drive shaft has to spin 3.73 times to rotate your tires once. Your tires are effectively another gear that needs to be turned and the larger the diameter, the more work it will take to turn them, just like on a bike. While weight will have some effect on your engine's ability to turn your tires, it is negligible compared to their size. Of course, I'm new to all this Jeep stuff, what would I know.
