The rear in the Rubicon is a 4.10 ratio. The standard rear is a 3.21, or 3.73 if you have the tow package.
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oh, and Brian. there's only one Manual tranny. (no pun intended) and it's a 6 speed. there are two auto trannys. 4 or 5 speed. probably paired to the 4 or 6 cyl motor.