How to: How to Stop a Loud Loco

With the motor gears they are easy enough to push on, but you have to be careful of not damaging the cog edges.
No glue need.  Watch the axle one with Harveys Coach.  These cogs are easy enough to put on with the right technique. 
I believe Super had a neat way of putting them on with a piece of wood with a hole in it and a clamp.  That is how I do it, but the hard part if getting the wheel off without breaking it.  Be careful of that job.