tail drive spur gear rubbing

[Kyle O.]

Hey guys, after getting some flying in this weekend.  I was looking over the heli, doing inspections here and there.  I noticed the 54 tooth spur gear seemed to be rubbing the transmission top bearing block.  There were signs of were the delrin gear had burs on the bottom side.  I feel i need to pull the main shaft out and see what i can find.  I dont feel any vertical play in the main shaft, and everything seems tight.  Again I did not build this heli, i bought it used.  Just wanted to see if anybody else may know whats wrong right off the bat.   Im guessing from looking at the manual, there may be a shim in the wrong spot or something. 

[Robert "Full" Montee]

In your investigation take a look at the orientation of part 320-303 and 320-302 in the transmission. Both can be reversed and this would cause 320-303 to come in contact with the 54t gear.

[Kyle O.]

I'm sorry guys, my mistake.  I looked again, and it's just normal gear wear between the hard coat spur and the big spur gear.