VEXpro ball shifter encoder issue

We are currently using the VEXpro ball shifter transmission, but when we drive the gears that are meant to act as feed back to the encoder lock up completely. We’ve tried backing off the gears from the housing slightly and it didn’t prove to make it any better. Is this a matter of improper assembly? Or has anyone else found a way to get them to spin smoothly after having them lock up?

Our team discovered this same problem with one of our two vex gearboxes on our drive train. After assembling our extra gearbox to test out our theory we could not find any other reason it would not spin corrector other then incorrect assembly. However, at this point almost all of our robot was assembled so we did not get a chance to look at the faulty gearbox on the bot so we are now only running one encoder. If you are in a situation where you can disassemble and try to identify any other problems I would love to hear if there are any other reasons this could be occurring.

We had this same problem. The only solution we found was to put super glue all the way around on the part of the large gear that fits into the gearbox. Make sure the super glue only goes on the right part before you insert it, so you don’t glue other things together. It isn’t the most elegant solution, but it worked.

Any chance you could post a photo?

Seizing gears, in any gearbox, are typically a sign of misaligned shafts. Misaligned shafts come from a couple of different places, including housing plates that aren’t perfectly parallel. In 2008, we replaced our SuperShifter housing with plastic spacers – since the plastic deformed under stress, the plates became non-parallel and the entire gearbox was incredibly inefficient.

Did you guys make sure that all of the gears seemed to free-spin properly prior to attaching the motors?

I didn’t assemble these transmissions personally. I didn’t want to go the super glue route yet because it’s very annoying to remove for something im not sure will work.

Hi Rodney,
I work for VEX Robotics – if you’re having trouble, is it possible you can give our support folks a buzz so they can try to help you out?

903.453.0802 or [email protected]

If you send in an email with a picture, that will help us understand what you’re describing.


We had this issue on our team. It’s not so much a shaft misalignment problem as the fact that over time, the large plastic gear’s press fit loosens up, and there’s enough friction between the bottom face of the gear and the side of the gearbox to stop if from moving sometimes. Supergluing the gear in really is the best solution. If you want to be able to get the gear out in the future, you can put some sort of shim under the gear while gluing; this will let you pry the gear out with some screwdrivers later.