Gearbox plunger issue gen 9

My gen 9 gear box runs fine…until I put my spring in the thing…then it’s just brrt brrt brrrt!
Stock or upgraded spring it grates and the plunger doesn’t move
Is it the motor height loading up the gears? My pistol grip has the base without the ability to adjust the height - should that be my first purchase - the rear teeth on the plunger have also become worn so should it be a new plunger?
Any ideas appreciated

pics…help allot

but if your ladder is worn it should be considered for replacement

have you tested with the stock spring?

what weight is the upgraded spring?

are all the other components stock?


Hi - yes everything is stock except for 1.3 uneven spring and green o ring
I have tried firing with stock and upgraded but with no luck
It runs great with no spring - plunger works smoothly when I manually inspect it - so I’m guessing it’s the ladder which is worn at the back end but I’m not sure - first blaster for me

yea…without putting too much thought into it…

looks likely your spring is providing enough tension to force the sector pickup to grind away (bbbrrrrrt) at the worn ladder.

grab a decent piston with a metal ladder and i expect you’ll be ok.

maybe a nice spring retainer too


Ok thankyou - I’ll give that a try

Check the teeth on your sector gear too!
It may have been damaged also!
Then when putting it back together check the contact of the 2 gears before closing it up.


Thanks for that - will do - I tried again just for hits and giggles and the plunger sometimes goes fully rearward but then gets stuck - I gather adjusting the motor height will also help it run smoothly once it runs?

Yep… I’d be checking that sector gear. Damaged teeth on the piston ladder usually means damaged sector gear.

If the pinion gear on your motor is too far engaged with your crown gear you’ll see that on a tear down pretty easily. Adjust your motor height in and out firing in between adjustments until you hit the sweetspot. You’ll hear it. Small adjustments at a time. :+1:

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Thanks will do👍🏻

The whole drive train works hardest at maximum spring compression.
I’m guessing that this is what the noise and the wear is telling you.
The motor is at its limit or the gear material has reached it’s peak elasticity and you need more torgue and stronger gears.

Sometimes however, it’s because the spring with thicker coils has reached full compression and there is just nowhere to go. If this is the case, changing to a more torquey motor or stronger gears may not help. The spring cannot compress further and something else will have to give or fail.

When the plunger sticks at the end, it’s usually because the motor has reached a stalemate with the spring. More torque please. :grimacing:


Yes I’ve ordered an adjustable bottom plate for the pistol grip as well to help this- along with metal gears, plunger etc👍🏻

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My guess is your battery Is low of charge or your trying to pull a 1.3 spring with a standard 7.4v battery?

Kane - I’ve tried it fresh off charge with a new battery and it grates so I don’t think it’s that

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I’m just wondering… if you fit an unequal spring backwards would it change the way the spring behaves? Not all, but most unequals have a compression bias.

Could be way off the mark here, but could your spring be binding on the retainer?


I’ll give it a go :man_shrugging:t2:

Nope - brrt brrt brrt
Waiting on parts now
Thanks for the input though - I’ve fast-tracked learning about blasters here

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