The area under the left-side bearing cup bore is recessed relative to the left-side cover parting surface. Any excess pressure used to seat the bearing cup into the bore can cause the housing to flex due to its large unsupported span. This flexing can lead to housing failure. GM-48008 rests on the bed of a hydraulic press and centers itself in the area under the bearing cup bore to provide a reaction surface during cup installation. Because GM-48008 is taller than the housing, contact is also prevented at the left cover parting surface. Using GM-48008 will prevent possible leaks at the cover mounting area and prevent catastrophic damage.