[vivek16]

1. NEVER EVER try and press on a gear without supporting the shaft itself (I drilled a tiny pocked into a small block of metal and used that on the back end of the shaft). The bearings in the fischer price aren't meant to take loads in that direction.

2. Make sure that the bore on your gear is right. I forget the exact size (I'm fairly positive that it's a 30 or a 32, measure the smooth part of the shaft to make sure). The splines on the shaft work real well for pressing on a gear.

With the right bore on the gear and the shaft supported, we were able to tap on the gear with a medium sized hammer. You'll want a socket or some sort of spacer to get the gear past the tip of the shaft.

EDIT: Our application was for a custom gearbox but it worked beautifully and no slippage occured. Use some medium-high strength loctite on your shaft.

-Vivek