You don't need to split the cases. The seal is only in the bottom case and is right on the outside of it too. It might not be that easy though. I've never had to do it, so someone else might be able to chime in too. You either need to get the seal out with the shaft still in place, or remove the clutch basket and pull the shift shaft out to have easy access to the seal. Like said ^^^^ I hope this makes sense cuz I got a good buzz goin lol