Let me start off by thanking everyone for giving me their opinions on my earlier questions. I just had a 2 1/2" spacer lift installed on my 2013 Rubicon Unlimited, along with Bilstein 5100 shocks and 35" BFG KO2 tires. I originally thought I had 4.10 gears, however it turned out that I have 3.73s. It now seems a little sluggish and my fuel consumption has dropped a couple of miles per gallon. Will it help at all to purchase the Flashpac to reprogram for tire size, speedometer and shifting points? I"m thinking a new gear set is probably what I need, just would rather not spend the money right now. If so, the question is, 4.10 or 4.56. This Jeep is my daily driver, however, I do go off road but not a rock crawler. I'm not sure if the 4.10 is enough lower to feel the difference. On the other hand, I don't want the rpms screaming on the freeway. Thanks for your thoughts.