Yes lower T- case gears , restored power like haveing a new engine .. but if its cost you go by its the locker its less than $200 and the 4.16 Tcase gears are over $400 , and I dont think the lower diff gears are even a concideration at this point , even for me, I have plenty of power and if I needed more , I would go for the 6.1 T-case gears ..