ok i have done this on my 94.. it had the allen screw and the hub popped off.. well i have to change the armature plate and figure i might as well change the fluid.. considering i have too.. anywho how to i fill it.. i havent even looked yet but is there that allen screw? and i noticed tho that my 99 has 2 screws holding the hub together instead of just popping off...

 

On the '99 Scrambler 400's I had, there was still the allen screw, and 3 small screws holding the hub cover on. On re-filling, believe you turn the hub with allen screw at line 3 or 9 o'clock for filling, when drips out then you're where the level should be