1999 Ford F Series Trucks Ring and Pinion Set F-350 Super Duty - RWD - Ford 10.5 in. Rear - Ring & Pinion Set - 4.88 Gear Ratio - 31 Spline Pinion - Rear guaranteed to replace your current 1999 Ford F Series Trucks Ring and Pinion Set F-350 Super Duty - RWD - Ford 10.5 in. Rear - Ring & Pinion Set - 4.88 Gear Ratio - 31 Spline Pinion - Rear. 1999 Ford F Series Trucks Ring and Pinion Set comes new OEM 1999 Ford F Series Trucks Ring and Pinion Set aftermarket new 1999 Ford F Series Trucks Ring and Pinion Set of remanufactured 1999 Ford F Series Trucks Ring and Pinion Set F-350 Super Duty - RWD - Ford 10.5 in. Rear - Ring & Pinion Set - 4.88 Gear Ratio - 31 Spline Pinion - Rear.