M4A1 Gen9 gearbox problem

Hi Guys, New here and after a bit of help

Chasing some info on how I might be able to fix this problem

You can see that little bearing turns itself over after about 3 shots.
I did notice before I shot it that the pin that goes through the gear and locates in the case was not flush with the top of the clear case. I have taken it apart upwards of ten time but get the same result every time I put it back together
I have ordered a nylon gearbox housing hoping that it might be a bit stronger.
Any help would be apreciated.


A bit of a zoom in to show it better.

When you put the gears back together and close up the case, is there a position that the the gears and ladder bar on the plunger must be in? I wandering if I am getting this config wrong and there is more force than usual and that is what is flexing the case and popping that bearing.

I couldn’t help my self, I pulled it apart again and reset all the gears.
You can see in these photos how the gear pin is just in the housing but not by much

I cant see any obvious bulges in the side of the case either.

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Shims mate. Gonna need to do some shimming. @LowGuido did a good video on that process.

Hey thanks for that watching it now.
I think the problem was that the trigger switch was not sitting flush and putting a bulge in the case near the sector gear pin
I sat it in flat and all looks good now but on the last trial before I figured out what was going it looks like that it has cracked the case from the where the sector gear pin sits to the trigger.
I got a nylon case coming so i will give the shims a go when I convert it over to metal gears.
Thanks for the help

Ok, got another problem now.
I got the Nylon gearbox today I pulled it all apart and made sure it was all good.
I started to put it all back together and slip in into the the receiver but this is where the problems start.
Its a really tight fit and when I do manage to push it in with heaps of force, the locating holes on the gearbox do not match up to the holes on the the receiver, I cant push it down or back anymore.
Here is a picture to better explain.

You can see the hole in the gearbox just barely visible.
Any help would be greatly appreciated.
I have had this blaster for 2 weeks now and only had one magazine or 5 minutes of use through it.
I just want to start enjoying it.

do you have photos of the gearbox outside of the housing??

it looks to me that is not a gen9 gearbox…

Hello chop ive been having problem with gen 9 trigger always tilted upwards , are you guys having the same issue too? Mind sharing the problems

@Zainul-Arifin_Zainul Did you want to start up a new topic and throw up some pics of the issue you’re experiencing mate.

Here are a couple photos of the gearbox

I just had an email back from the seller.
They reckon that mods will have to be done to it to make it fit.
I think it might be dremel time over the weekend.
Bit of a shame that it doesnt fit out of the box.

I just ordered another nylon shell that looks a bit different to the one i got. The new one has a cut out at the back where the spring is. The one i have now doesnt.
Hopefully this fits.

Hopefully this may help someone in the future.
Pretty much the seller doesn’t want anything to do with helping me to get this gear box to fit.
This is the one I purchased that does not fit unless you want to shave and re sculpture the case.

You can see it doesn’t have the screw flange on top (1), it doesn’t have the cut out window at the back of the spring (2). It doesn’t have the same curved shape at the back of the handle grip (3) and it doesn’t have the same battery plug (4) I’m pretty sure that the incorrect handle shape (3) is the difference that is causing the problem of it not fitting in the Gen9 housing.

This is the new nylon one that I have just ordered this morning.

You can see it is pretty much a direct copy of the standard clear one.

It is not due to be delivered until next Friday so stay tuned and hopefully this one fits.
Meanwhile the shim set, metal gears, 1.3 spring and 7mm bearings should all be here before the case so when it does rock up I will have all the parts to build it properly.

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So, that last one you pictured is a gen9 box.
Im not sure what blaster the other one is supposed to fit, but it looks a little like a type2.

Yep ebay listing said for gen9 but when I questioned the fitment the seller said it will need modification to fit the M4 gen9
This is the listing

That last picture of the gearbox with the screws sat next to it is the one I have ordered after ordering the one in the link above that doesn’t fit.

Hi Matt, I ordered the same useless nylon gearbox it seems but from AliExpress. I had my doubts but a lot of sellers are claiming it could fit the gen 9. Not one complaint from buyers. Then I saw this page.

Here’s the link to the AliExpress listing

Upgrade Nylon No.2 Gearbox for JinMing 9th Gen9 M4A1/LDT416 Gel Ball for Blaster Toy

KIm ordering this one, even though it looks horrible:

31% Off | Water Gel Beads Parts Nylon Strengthen Gearbox Shell Cover for JM Gen.9 Gearbox Modification Upgrade - Black

Any alternatives?

Found this:

Original Gearbox Shell for JM Gen.8 M-4A1 Water Gel Beads Blaster Replacement Decoration For Gel Ball Blaster Modification

Looks more like gen 9 but product description says gen 8. ¯_(ツ)_/¯

Complete gearbox

Gday mate u not in perth by anychance i have made contact with a guy that is modding my M4 gen9, I should be picking it up today.