Anyone have any tips for removing the variable belt drive pulley on a Polaris 400 ?

This triangle shaped drive hub is threaded on the engine output shaft. Any ideas on how to turn this while holding the engine from turning?

 I thought about welding up  a triangle shaped driver that would fit tight on the 3 flats of this drive hub with a bolt on it that I could use an impact on to try and loosen it up . It's aluminum so I really don't want to torque too much on it. I thought some gentle tapping with a impact might get it loose.

 All this so I can get the back of the belt guard off so I can get the transmission out. It's locked in low and I can't use reverse or high range.

 Anybody have any experience or knowledge about what can go wrong with the shifting mechanism inside the transmission case or have any sort of exploded view drawing they can share.

Any help or input would be greatly appreciated.

(Drive Pulley (2).jpg)

Drive Pulley (2).jpg (98KB - 475 downloads)