Press fitting a pinion gear on a Neo

Has anyone tried press fitting a gear on a Neo Brushless yet? If so, what worked for you?

After last years pain with pressing on gear on MiniCIMs we didn’t take the chance.

We used emery cloth on the inside of the gear and on the shaft of the motor to reduce the amount of pressure required, not as much as on the Min’s. We used retaining compound to ensure a good tight connection.

It worked without difficulty. I’m not brave enough to do it the regular way but I think it would work better than on the Mini’s.

I would suggest taking the back casing off the motor, there’s a few screws around the casing to do so. Then you can easily support the back of the shaft. @Greg_Needel might have more advice but barring that, that’s how I’d do it.


We got one open but then stripped a screw on the second and called time out. That Loctite on those little screws is something else.

We’ve press fitted pinion gears for the CIM Sports onto 2 neo motors so far without any issues. We didn’t take off back casing or anything.

The recommendation is to take the back can off using a high quality 1.5mm allen key. The screws holding the can on do have locktite on them but can be removed.

Ok, that sounds about right, high quality being the issue we’re seeing.

Guide is up for the pinion gear pressing process. Make sure to use a high quality 1.5mm Allen key as the screws have locktite on them.

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We are building a test drivetrain this week and are having the opposite problem – the Vex pinion gears (217-3099 in particular) slide on without any pressure and the retaining clips just pop off if you apply any pressure to them - we can’t get them to bite down no matter which way they are installed. Anyone have ideas on how to get them to stay?

217-3099 should not be a press fit. Perhaps the retaining rings you are using are to large? Maybe try these?


You could use a bit of loctite bearing retaining compound.
Warning: It will not come off again without a press and probably heat. The retaining clips are intended to be single use. Especially if you forced them on backwards. They might have limited bite on a hardened shaft, but there should not be a lot of thrust load on a spur gear. The 5/16th D ones you get at the hardware store or McMasterCarr are close enough to 8mm.


All of the hype about pressed-on pinions and the fact that the very first one we put on a Neo today required quite a bit of force had us confused when the rest of them just slid on.

The ones we had were pretty loose so we ordered some from McMaster after not being able to find them locally. We got them to lock in place, finally, after doubling them up. If we have additional issues we will add some of the loctite.

Thanks to both of you!

Now, if only I’d ordered the correct bore gears for the gearbox we’d almost have a functional drive base in a day (gotta wait for Vex to open again after New Years).