there really are none that i can think of, overdrive affects 5th gear while towing. turning o/d off basically eliminates that last gear so that you dont put excessive strain on the trans from shifting back and forth so much.

on another note, removing the fuse for the abs is highly recommended by me and many others due to the fact that it really serves no purpose off road and can often times put you in a tight spot.

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2001 Ford Ranger Supercab (4dr), Oxford White, 4.0 Sohc, 4x4, Manual trans (hurst equipped), 4:10's, 3" body lift.