FYI, I had the same question when I bought mine. You want the 3.73 and down Eaton even if you are installing larger gears than a 3.73 because JKs have thicker gears. Confusing yes. I would call Marcus also.
Also, I did the Eaton in the front that used 30 spline shafts instead of 27 spline. Upgraded the axles and cyro froze the gear set.
2008 Jeep JK Unlimited. Auto. Mods: 3.5 RK Max Travel Kit, RK tie rod. 35" Nitto Trail Grappers. Eaton 4 Pinion E-Lockers front and rear. Nitro 30 spline chrome moly front axles. Yukon 5.13 gears/Cyrotreated. Sleeved and gusseted front axle. Dynatrac ball joints. Mopar big brake kit, Advance Adaptors 4wd shift linkage, Tom Woods front and rear driveshaft. Ace Rock Sliders. Terra Flex hinged tire carrier, Carolina Metal Masters grab bars. Exp One Frt Bumper. Warn Zeon 12 Winch.
Last edited by Poormanz28; 02-24-2015 at 06:52 AM.