What kind of oil goes in rearend and transmission of a 1999 sportsman 4x4?

For a 1999 Polaris Sportsman 4x4, the rear differential typically uses a hypoid gear oil, commonly recommended as 75W-90 or 80W-90. For the transmission, you should use a Polaris Transmission Fluid or a suitable equivalent, often specified as ATF (Automatic Transmission Fluid). Always check the owner's manual for specific recommendations to ensure optimal performance.