V2 gearbox help
 

I recently aquired a G&G GR4 CQB, the gun needs a fair amount of work. I just rewired the entire gearbox, put it back together to see if it worked and it didn't fire. I took the motor out far enough so it wasn't hitting the other gears and it is working great.

so it's getting power. I tried playing with the grip screw to back it off a bit thinking it was too tight and it just makes that grinding sound when it's not fulling engaging the gears. tightened it a little bit and then just clicks when I pull the trigger. I can only get it to do either or but not actually fire.

Any suggestions on what should be my next step?

Several possibilities here.

Try a powerful battery, another motor, a circuit tester to see how much power loss there is between battery and motor.

no luck there, tried another motor same thing. Motor works in my other AEG. checked wiring, it's all good.

also tried with the piston and spring out, didn't make a difference. gears are moving easy when I move them with my finger when the gearbox is assembled without piston

Did you reshim it? Perhaps you did it too tightly if you did.
When you're turning the gears by hand is the mechbox screwed down?

Motor connected the right way (pos-pos/neg-neg)? AV latch reversed?

when turning the gears by hand it is screwed down. also motor is hooked up correctly.

some progress has been made. I reshimmed the gears again. Took out the piston and cylinder just to see if I could get the gears turning with the power from the motor. so I eventually got the gears turning. Now I'm thinking this has to be it, but no. I put the piston and cylinder in and the click is back. Now I pull the trigger and I get nothing.

Any ideas on what I should try next?

What battery are you using (all details) and what power spring?
Might just be your battery vs spring power.

I was using an 8.4v 1400mah, and have no idea what the spring is. I have a M110 so I'll probably throw that in just to see what's up, and I'll try my 9.6 and see where that gets me

Try a large type battery. If that works (or your 9.6v mini works) then you don't have enough power to pull the spring.