1991 Ford F Series Trucks Ring and Pinion Set F-350 - Ford 10.25 in. Rear - Ring and Pinion Set - 3.73 Ratio - 1.5 in. Long Pinion Spline - Rear guaranteed to replace your current 1991 Ford F Series Trucks Ring and Pinion Set F-350 - Ford 10.25 in. Rear - Ring and Pinion Set - 3.73 Ratio - 1.5 in. Long Pinion Spline - Rear. 1991 Ford F Series Trucks Ring and Pinion Set comes new OEM 1991 Ford F Series Trucks Ring and Pinion Set aftermarket new 1991 Ford F Series Trucks Ring and Pinion Set of remanufactured 1991 Ford F Series Trucks Ring and Pinion Set F-350 - Ford 10.25 in. Rear - Ring and Pinion Set - 3.73 Ratio - 1.5 in. Long Pinion Spline - Rear.