Anyone done a Hydro Gear output gear change out?

[953 nut 55,039]

I have a GT 14 with a Hydro Gear motor with bad releaf valves in the Acceleration Valve area, I would like to replace it with a good unit from a Ranger. The output drive gear is not the same on the two motors and I was wondering if anyone could give me some guidance on changing the gears. The manual has NOTHING on this. Thanks.    

[Ole MN 11]

Yes I changed one out a few years ago. The only thing that sticks out in my mind was the needle bearings. Any way it was not to hard to do and i'm still using that hydro today.