The rear crankshaft seal for SGE may be one of two designs in production; however, either design can be used for service. The service seal must be installed to a specific depth below flush on the rear cover. GM-51369 installs the new seal to this particular depth, piloting the seal onto the rear of the crankshaft and seating the ID & OD of the seal to prevent damage and ensure the seal is at the correct depth. Unapproved methods may result in a seal life that is less than designed and customer dissatisfaction.