2012 Sportsman 400/500 and EFI Tractor Service Manual 9923412, Page 285Get this manual
FINAL DRIVE 6Place ADC Piston Tool PA-48542 on top of the piston and verify alignment of the sight hole (circled) and piston mark with the casting marksSupport the case and press the piston down evenlyThe piston is fully seated and located in the pin bosses when the piston surface is just below the cavity edge
Assembly
1Thoroughly clean the gearcase components before beginning reassembly2Install new seal in the main gearcase halve3Install the input shaft assemblyInstall the pinion gear bearing assembly (1)Install new seal and oring the input shaft cover (2) prior to reassembly1 2