Originally Posted by goodysgotacuda
4.88s will be about right with 37s, so if you plan on that down the road..go that route. If not, 4.56 would be better suited for 35s IMO. My 4.88s w/37s buzzes too high for me on the highway.
Are you saying that your rpms are higher than you would like on the highway with 4.88 gears and 37" tires?
I agree that 4.88 is a good choice for a 37" tire and 4.56 would work for a 35" or a 37" tire. The 4.88 gear may be too much for 35" tires on a daily driver at least for a 2012+ with an auto transmission. On a 6 speed manual, your rpms will run about 100 rpm less than the auto in the top gear, so you have a little lower rpms.
I'm running 4.56 gears with 35" tires and at 70 mph, my rpms are slightly out of the green ECO marks on the tach. I think I'm running about 2600 rpm at 70 mph, but my 35" BFG KM2 tires are closer to 34". If I had a manual transmission, my highway rpms would be about 2500 with 4.56 gears. IMO, the 4.56 gears are almost too much for a 35" tire if you do a lot of highway driving.
I didn't have any problem with my 4.10 Rubicon gears with 35" tires, but because of adding extra weight on my JKU including significantly heavier axles and getting ready for 37" tires, I moved up to 4.56 gears. My rpms should drop back into the ECO area of the tach at about 2400 rpm when I do the tire swap.