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Gearbox problem...

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Hi, guys I'm new to this website. Played airsoft for 2 years now and do all my repairs.

But recently I had to replace my gearbox has last one was broken( ill try and keep this short :) )

Basically everything was removed from broken gearbox to new one. Shimming looked good everything else seems ok ,so I put gearbox together attach pistol grip and motor to test fire. And I get a noise has if the motor isn't in positioned correctly, but it is. In further inspection I can see on the outside of gearbox the bushes moving except the selector gear it seems jamed. I have look inside many times and it seems to clear the trigger guard reverse block? I forget what it's called...so I have stumbled upon a probably silly problem but I can't get my head round it. Any ideas? Anything is mush appreciated.

Using a 7.4lipo

G&p gearbox

Shs internals with src gears

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Have you got the motor height too high or too low? Changing to a different gearbox casing can alter the amount the motor needs to be inserted to make contact with the gears. Try first unwinding the screw in the centre of the motor plate. If it spins on auto, but doesn't move the gears, slowly turn it in and test fire every full turn until it does, then keep on turning in with it running on auto until it makes a screeching noise and slows right down, then back off one turn or until you have a nice smooth sounding cycle.


If that's not it, check that the Sector gear is meeting the teeth on the back of the piston correctly. It could be the piston sits a couple of mm too deep in the cylinder, making the first sector gear tooth dig into the bottom of the rear piston tooth instead of against the front of it. That could jam it up. Try it with the top cover of the gearbox off and turn the gears whilst holding the piston the the fully home position with your finger (instead of with the spring) as that should show where the first contact point is.

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