It’s currently got the factory 3.73 gears in the differentials but after a routine check the other day it was discovered that the popping noise I hear during acceleration was not the u-joints but it is the rear ring and pinion gears wearing out. I currently have a 4″ pro comp lift on my TJ and it’s got 33×10.5 KM2′s. The tires only have 6,500 miles on them but I already know that when they are worn down I am going to go up to 35×12.5 tires, probably KM2′s again. I put a lot of miles on my Jeep so the new tires aren’t many years away, probably about a year and a half. I’ve only had the Wrangler for 21 months and I’ve run it up from 77,000 miles to 116,000 miles after all.
Anyways back on track. I was thinking that because I am going to go up to 35′s in the not-so-distant future, I should probably go ahead and put the gears in that will work best with those instead of the best for the 33″ tires. Yes I know my gas mileage will be worse but it will have more power too for the time being. Would 4.56 be a good choice? It is my daily driver so I don’t want to go crazy with the low end power but lose top end speed, a lot of my driving is on the highway. That is a bit of a problem I am experiencing right now is that I get 11 mpg with the 3.73 gears because on the highway I have to down shift to 4th just to maintain a speed above 65 going up any kind of hill or into any breeze. It has the 4.0L engine too.
if you plan to go up to 35″ rubbers I would regear now to 4.56.
there is no reason that you cant run stock gears with 35s and if you re-gear and get bigger tires you will see a huge drop in your mpg if your going to daily drive it i would stay stock or… if you can afford it buy another Jeep on stock tires and put 5.29 gears and 36′s on this one
Are you planning to offroad it at all? There’s no way I’ll ever offroad a D-35 with anything bigger than 31″s on it. That axle just won’t stand up to the extra weight and torque of tires that big offroad. All you need to do is get them spinning, then suddenly get traction, and BOOM, your day is ruined.
A Ford 8.8 is a fairly easy conversion, you can get one out of an explorer for short money, and you get the added benefit of rear disc brakes.
As far as gear ratios go, there are plenty of charts online. For a daily driver that does some offroading, for 33″ you want to go 4.10 or 4.56. For 35″, 4.56 minimum, 4.88 or even 5.13 if you can get them.