Does anyone know what the threads on the mounting holes for the AM snowblower motor are?
Does anyone have any recommendations when using these motors? I don’t have any experience with them.
I believe the snow blower motor uses a 10-32 screw.
Why would you use this motor when there are plenty of better motors available?
Price, ease-of-use, and availability I can think of as reasons, but I do agree that using a versaplanetary with a more powerful motor would be a better option functionally.
The mounting holes are either M5 or 10-32 according to the CAD model, most likely M5 (the model reads 0.1969"). Try both and see what works. Make sure whoever is doing it does not attempt to force a screw into the holes. 
Chances are they already have them.
Free Solution vs. $$$ Solution
It depends on resource level for which you decide.
I can see that but in this point in time, there are a decent amount of other solutions that don’t cost much. You also have to factor in ease of use, replacements, reliability, cost per match and other factors. I would personally pass on this motor and move to something else for a FRC competition robot.
The internal worm drive is a nice advantage of the snow blower motor. Any other motor plus an off the shelf worm gearbox can get quite large and expensive. If you don’t need a ton of power in a mechanism, then it isn’t a bad option.
So we’re talking about a mechanism that needs to resist back driving. I understand the concerns about this motor (trust me, I’d rather not use it) but cost and weight are an issue at this point.
Are there any other options that I’m not thinking of that would use a higher-power setup without being able to be back driven? This is an application where we can’t just latch the mechanism in position and release with a servo or air cylinder.
In case you were wondering, no, this is not for a scaling mechanism.
It’s hard to recommend options that don’t backdrive without knowing your application, since it really does vary. If it’s a winch and release mechanism, like a spring loaded shooter, it can be as simple as throwing a Craftsman wrench on one of your hex shafts for a makeshift ratchet. This is more difficult if your mechanism needs to be powered in more than one direction, obviously, but it’s one simple solution.
Does it need to hold position when the robot is disabled? If it isn’t a scaling mechanism I don’t see why it would. Things like arms can, if well designed, be lightly stalled in order to hold position for short durations. You don’t necessarily need a mechanical brake for these to work.
You could also modify old window motors you already have. I know of a team that plugged a BAG motor into a window motor gearbox for an anti-backdrive mechanism.
The motor has 70 in-lb thats not no power. We are looking at it through a 10:1 Gearbox to get some power low speed from it.
Back to the OP - The screws are 10-32, same as used on a CIM.
“The motor has 70 in-lb thats not no power. We are looking at it through a 10:1 Gearbox to get some power low speed from it.”
The 70 in-lbs is the stall torque at zero rpm. You should plan to use half of that if you want to do any useful work.
The free speed is already only 100 rpm. With a 10:1 gearbox that’s down to 10 rpm max (or 1/6 rotation per second). At half load speed your looking at closer to 1/12 of a rotation per second. Probably way to slow to climb with.
Maybe I over read something. Are they climbing with this motor? We are not climbing ours is for a Choo Choo.