I have a 91 300 fourtrax and am changing the gear case oils. I changed the front and rear and as far as the one in the middle on the left side, is the drain plug the one that says " check "?? I think its a 10ml. bolt. Also where is the fill line?? It says at the top of the case 200cm3 or something. Thanks.

 

You need to get an owners manual! There is a large one on top, that is the fill hole. There is one on the very bottom (side), that is the drain hole. The one in the middle that says "check" is just what it says.

First, ride the bike a while to heat up the oil so it flows better. Remove the fill cap and then the drain plug, and let it drain thoroughly. Replace the drain plug, and remove the check bolt. Slowly fill with oil until you just see a little oil coming from the check bolt hole. Replace the check bolt and fill cap, and take the bike for a short ride. Then, recheck the oil level. If a tiny bit of oil isn't coming from the check bolt hole, add a little.

My choice in oils for my diffs is Mobil 1 75W90 synthetic.

 

Thanks for the reply, i am trying to find a manual and also trying to get ready for a atv rally in a few days so bear with me. I couldnt find the drain hole on that one, but i'll look again tonight. So i suppose i use the same gear oil i used for the front and rear difs? I used the gear oil that was printed on the gear cases. ( hypoid 80W-90 )