2001-Later GMT800, 2500HD, 3500 with 6.6 liter Duramax diesel engine The rear seal is press fitted to both the engine block and crankshaft. Through testing, it has been determined the common practice of prying seals from the block is not acceptable due to potential damage to the block and crankshaft. GM-44641 is a special puller with three jaws designed to grab the inner lip of the seal. The forcing screw attached to the center plate is used to react against the crankshaft end to pull the seal out.