Читать книгу Ford Differentials - Joseph Palazzolo - Страница 12

The 9-inch’s very large pinion offset of 2.25 inches requires the pinion to be straddle mounted, which refers to the fact the pinion head has bearings that straddle it on either side. There is a machined roller bearing race on the pinion head portion that points at the differential opposite the tapered bearing races. This additional bearing and, more importantly, the necessary casting support structure is what drives the larger hypoid offset. The additional straddle mount pocket bearing provides additional support to the pinion head during high-torque events. This bearing is one of the reasons that the 9-inch has the reputation for being bulletproof.

There are three bearings on the pinion shaft: the two traditional tapered roller bearings for the head and tail bearings with a third cylindrical roller bearing on the opposite end of the pinion head. In order to allow for the additional straddle mounted bearing and casting support structure, the hypoid offset needs to be large enough to clear the differential case. Hypoid offset is the distance between the centerline of the pinion and the centerline of the ring gear. This is 2.25 inches for the Ford 9-inch and 1.5 inches for the 8.8-inch axle.