im having gear oil come out of the top-end(under the gas tank) of the tube that runs from the rear gear casing.what would be causing this?

 

Are you speaking of oil coming out a vent tube for the rear differential? If so, it is way too full, most likely.

 

I had a '98 Grizzly and my brother had a '99 that did the same thing. We discovered that if you fill the rear differential up to the top of the fill hole, it was too much oil when doing high speed runs and it work it's way up the breather tube and discharge at or near the exhaust pipe at the fuel tank. The dealer suggested that we measure exactly the amount of oil as shown in the manual and only install that amount. Once we did this, the problem did stop. We never had this happen with the front differential at all. Hope this helps.

 

yep that help alot thanks. the dealer told me to fill it till it just starts to run over