I'm running 305/45/22 tires. The truck did have 3.55 gears and would lug up hills and when the cruise control was set it would kick down going up hills(sucks gas). With the 4.56 it does not kick down anymore and just over comes the hills (saves gas). I was a hardcore member of Dodgetalk.com for a while and a lot of the guys switched to 4.56 because the trucks have OD and it helped the situation a bunch. Most of them had the stock 20" wheels. It has been mentioned that Dodge should have at least installed 4.10 gears in there trucks and that would have better than the 3.55 gears. Mainly because they have OD transmissions and when you ad the .75 OD ratio it equals out to be like 3.89 gear ( or close to that with the 4.56 gears). I have not did the math in awhile but you get the idea. Tows better to. With the 15" tires and the 4.10 you have you should be close to what I'm running if you know what I mean.