It's not about 3,000 rpm, it's about being in your powerband at average road speeds, if it takes your car 37 mph to just reach 3,000 rpm then 6,000 rpm is gonna be twice the mph (74 mph). If your powerband is 3,000-6,000 rpm you got to be going 37-74 mph in 1st, 2nd is gonna be a bunch of more mph, where as 5.13 (not saying to run them just an eg.) only needs 20-40 mph to cover 3,000-6,000 rpm powerband. But like I'm pointing out 3.91's is about 50% of the gear ratio different but lowers the needed mph by about 65% 26-52 mph for 3,000-6,000 rpm, 3.55 = 28.5-57 mph which is about half way 2.76 = 37-74 mph vs 5.13 = 20-40 mph.