Remove the tailhousing/retainer seal with a suitable puller or by tapping at the seal's outermost edge while staying clear of the aluminum retainer material. Use an eye-type snap-ring tool for this snap ring. (This internal snap ring requires a heavy-duty tool designed for internal snap rings.) Use the correct tool. The rear retainer tailhousing is aluminum and will not tolerate prying with screwdrivers or awls. Protect the aluminum castings.