84 928 5 speed
 

Hi everyone , My 928S 5 speed with 42k miles suddenly would not go into fifth gear , I removed the trans axle, disassembled it down to the gearing, I have a tranny shop but never worked on one of these. I cannot figure out how to remove the upper 5Th gear . I loosened the 54MM nut on the pinion shaft but it bottoms out . Is anyone familiar with this transmission. Alldata has no technical info .

Thanks in advance.