does anyone know how often and how to refill the gearcase oil??
Matto

 

I would recommend annualy, maybe every other year if you don't ride many miles and don't go through much slop, maybe 2 times a year if you like to go through water a lot.
What model do you have? They have different fill locations and amounts for different models (Sportsmans, Magnums, etc). The owner's manual should tell you where the fill opening is and how much to fill it.

 

I change mine twice a year and use POLARIS oil. Not a problem since 1993 so I must be doing it right.