3.21 gearing, from what ive been reading for the last year, will be totally fine with 33" tires. 3.73 would be better, but for 33" tires and the new Pentastar Engine, your set. The general rule is: 31-33" (3.23-3.73) 35(4.57 and up)rlpickering13 said:Guys, I am getting ready to buy a new 2013 Jeep, I want a base model sport that I can upgrade myself, I have been looking at several base sport models with 3.73 gearing but I have found a few with 3.21 that I can get for $20,000 flat. Wanted your thoughts, I will be upgrading the tires and rims to 15" rims with 33x12.5 tires. Will not be doing any heavy off roading just logging roads and hunting trails do you think the 3.21 will be a big deal.