1981 Ford F Series Trucks Ring and Pinion Set F-150 - RWD - Ford 9 in. - Ring and Pinion Set - 4.86 Ratio - 9310 Pro Gear - Oversized 35 Spline Pinion - Rear guaranteed to replace your current 1981 Ford F Series Trucks Ring and Pinion Set F-150 - RWD - Ford 9 in. - Ring and Pinion Set - 4.86 Ratio - 9310 Pro Gear - Oversized 35 Spline Pinion - Rear. 1981 Ford F Series Trucks Ring and Pinion Set comes new OEM 1981 Ford F Series Trucks Ring and Pinion Set aftermarket new 1981 Ford F Series Trucks Ring and Pinion Set of remanufactured 1981 Ford F Series Trucks Ring and Pinion Set F-150 - RWD - Ford 9 in. - Ring and Pinion Set - 4.86 Ratio - 9310 Pro Gear - Oversized 35 Spline Pinion - Rear.