It makes more sense when you look at the back of the crankshaft. There are two machined surfaces in the back of the crank, and they will accept both large and small diameter pilot bearings. The smaller of the two is deeper in the crankshaft by nearly 3/4 inch, and this is the one we installed. As a result the transmission input shaft was just barely engaging the pilot bearing, and the vibration caused the bearing to eventually walk its way out of the crank. Fortunately, this was caught before any real damage occurred to the tranny.