It takes a small metric Hex key type allen wrench to loosen a set screw on the collar. Move it to whatever position you like or remove it. Whatever.
Here is the high speed collar...
http://www.horizonhobby.com/Shop/ByC...dID=EVO100834A
Here is the low speed collar....
http://www.horizonhobby.com/Shop/ByC...dID=EVO100850A
You can see the set screw on each one.
Enjoy,
Jim