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Version 7(Marui M14 series) Gearbox Guide

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#1 SpentBrass

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Posted 11 May 2007 - 08:32 PM

Version 7 Gearbox Takedown/Maintenance Guide

by Spentbrass

*Disclaimer: This guide is for informational purposes only. It is not 100% correct or complete, and is not intended to be a end-all step by step guide. After using my gun to make this guide I completely reassembled it as seen in the pictures, and it works perfectly. If you use this guide and find your gun no longer works, I will not be held liable, though feel free to contact me and I will help you in any way I can.*


This is a guide to help in the takedown, maintainance, upgrading, and reassembly of the Version 7 gearbox, which is used by all the guns in the Tokyo Marui M-14 AEG series (M14 Wood version, OD version, SOCOM version). At the time of this writing, these are the only guns in production by any manufacturer which use this gearbox design. There are several TM "clone" M-14's made by chinese companies, but these do not use 100% true version 7 gearboxes, so part or all of this guide may not apply to them.

This guide does not include an explaination of how to break the gun down to the gearbox its self, there are a few reasons for this: If you cant figure out how to get to the gearbox fairly easily, disassembly of the gearbox its self may be too complex for your skill level. If this is the case i would reccomend taking your gun to a qualified airsmith instead of going the DIY route. hat being said, it really isnt hard to do at all, and most people should be able to do it themselves fairly easily. Lastly, I just really didnt feel like taking the extra pictures

One area you may find frustrating however is this screw right here:

It must be removed to seperate the gearbox from the receiver. Its just unobtrusive enough to make you confused as to why you cant get your gearbox out of the damn receiver. It is covered by the bolt catch which is secured by a small pin.

Now, to start with, your gearbox should look like this:

We will start on the left side. The first thing we have to do is remove the metal plate holding all those complicated little thingamabobs down. Start by finding a peice of cardboard, and poking four holes in it with a screwdriver. One hole for each screw. Label the holes as the picture shows, this will help with reassembly later.

Now remove the screws, taking care not to lift the metal plate off yet. There are a few tiny-ass spring you wont want flying out. After the screws are out, place them in their corresponding holes on the cardboard.

Alright, after that is done, we have to get these tiny springs off.

!WARNING! DO NOT LOOSE THOSE SPRINGS. Your gun will NOT work without them. I dont know of anyhwere you can get replacements short of contacting TM themselves, so be extra careful.

I would reccomend using a small flathead screwdriver for this. Carefully lift one end of the spring off of one of the little hooks its holding on to. Again, be careful. Repeat process with the other spring. Put them in a safe place. I personally use small cups and bowls to hold small parts.

Now, lift the metal plate off of the left side. Nothing should spring off, but be careful anyway. You should be greeted by this:

Remove the grey metal peices, they should just pop right out of place. Put them aside. Next take the electrical contact assembly off. It just kind of sits on there with one plastic peg in a hole, so it just come off. Be gentle with this peice, its a bit on the fragile side.

End of Section one. Please hold posts untill im done. Send comments via PM.

#2 Comrade_MP

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Posted 11 May 2007 - 09:52 PM

Nice,nice, since i've seen some pic of the M14 taken down, I've wondered about the gearbox. Can we expect some uber clear pics?

#3 SpentBrass

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Posted 11 May 2007 - 10:05 PM


#4 SpentBrass

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Posted 12 May 2007 - 01:25 AM

Section Two

At this point, the left side of your gearbox should look like this (look at those nasty nylon bushings..):

Next, disconnect the wiring from the motor. The connectors should slip off the motor with a little tug.


Moving on to the right side of the gearbox now. We must begin by removing the selector switch. To do this, unscrew the two small screws to the left and right of the switch.

WARNING! After you take off the switch, watch out for this tiny spring.

Its important and if you loose it, life will suck. Under it is a tiny ball detent, dont loose that either.

Next, we have to take these two screws out so we can remove the rest of the electrical asssembly.


After those two screws are out, the rest of the electrical assembly should pop off. It holds on to the trigger, so you may need to use a small screwdriver to kinda pry it up.

After its off, set it aside.

Next, we go back to the left side of the gun to take the selector transfer bar off. Just lift it up over the metal peice and slide it off. Its not incredibly tough plastic, so dont abuse it.

Now on to the trigger. All you have to do is take off this spring. Its held on in a similar way to the two tiny ones. Lift it off one of the hooks, carefully remove, place aside.

The last thing on the right side is the safety. Remove this screw, lift it up, shouldnt be hard.

Posted Image

At this point, you should be down to the bare gearbox its self.

Posted Image

A sexier gearbox, you will never find. End of Section two. Section three soon to come.

#5 SpentBrass

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Posted 12 May 2007 - 03:08 PM

Section three.

Alright, now its time to remove the motor mount from the rest of the gearbox shell. Lets start by making a screw guide similar to the one we made earlier. For this, instead of labeling the holes, simply draw out a shape similar to the shape of the gearbox.

Now, lets remove the motor mount screws and place them in the screw guide. These screws are torx head screws, and therefore you will need a special screwdriver to remove them. You should be able to find a good torx head screwdriver set at any hardware store.

Remember, the screws should have small washers on them, try not to loose the washers.

After the screws are removed, the motor mount should simply slide out.

Now we must remove the rest of the screws from the gearbox shell. Unscrew, place in the screw guide.

after all the screws are removed, the last thing holding your gearbox together will be this peice of metal that is slid over a rail on the top of the gearbox (simlar to a Version 3 gearbox).

Just slide it backwards and off the gun. This may require a bit of force. Be careful not to let the gearbox fly apart after this is off. It probably wont without a serious jolt, but be careful.

Now we commence the opening of the gearbox. To do this, you need to keep the mainspring from flying out, taking the spring guide and probably other stuff with it. The easiest way to do this is to insert a screwdriver into the hole in the back of the gearbox, and use it to hold the spring down while you lift the side of the gearbox shell off.

Insert screwdriver (i used a diferent one when I actually opened it)

While holding the spring down with the screwdriver, lift the gearbox shell up, but not off. Pulling up from where the motor mount enters the shell should work.

Before we lift the shell all the way off, lift the screwdriver up carefully and let the spring guide/spring out of the back of the gearbox.

End of Section three

#6 SpentBrass

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Posted 12 May 2007 - 04:00 PM

Section four

Now we are ready to lift the gearbox shell off. After its off, you should see this.

Except your gun will probably have a stock spring in it, which looks like this:
Stock M14 spring on bottom, ~350 FPS upgrade spring on top. The stock spring is attached to the piston.

Now, lets start taking parts out for cleaning/ repalcement.

Im going to be replacing my stock nylon bushings with a set of systema metal bushings. Stock on top, Systema below.

First, lets take out the piston. If your gun is stock, that silver spring will be attached to the piston. Slide the piston out of the cylinder, set it aside.

Now lift the cylinder/tappet plate/ air nozzel out in one peice. be creful not to loose the spring under the tappet plate.

Now on to the gears. These are basicly the same as V2/3 marui gears, but downsized a bit. They are made of the same fairly crappy zinc alloy, and should be replaced with a steel gear set ASAP if you upgrade your ROF or spring power.


Im no expert on shimming, but from what I understand, the shims are spacers that go on the axles to keep the gears evenly spaced so that they line up with each other and the piston teeth so as to cause the least amount of friction possible. I would reccomend looking up a few guides on shimming before moving your shims around. if you dont replace any gears or bushings, the stock shim job should do fine, so take note of what size and type of shim each gear has on each side so that you can redo the stock shim job when you reassemble the gearbox.

First, take out the bevel gear.

Under the bevel gear is the anti-reversal latch. It has a very tiny spring on it, which you should be careful not to loose. Take the anti-reversal latch w/spring out and set it aside.

Now take out the sector gear, its the one on the right. (sorry for the bad focus)

And finally, take out the spur gear. its the flat one in the middle (and by process of elimination, the only one you havent taken out )

Posted Image

End of Section four

#7 SpentBrass

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Posted 12 May 2007 - 04:59 PM

Section five.

Now we should have everything out of the gearbox shell except for the bushings.

Use a screwdriver or pen to pop them out from the outside.

After the bushings are out, use a paper towell or something, and clean all of the gunk and old grease out of the gearbox.

Now we need to clean and regrease the parts.

For this I will be using White Lithium Grease. It is avaialble at any hardware store for like $2. If you can, I would reccomend you use CA Cylinder and Gear grease, as it is designed for use in AEG's whereas WLG isnt, though it works fine and wont cause any problems.

Start by cleaning your bushings and putting them back in. Lube them a little to help keep them in place.

Now lets put the shims back on the gears (in the same way as stock or redone your way if you feel up to it). and regrease the gears. Ignore the bushings on my gears. The systema bushings were a very tight fit over the axle of the gear, so I had to leave them on both sides. Stock bushings should remain in the gearbox shell and not stuck to the gear axle.

Bevel bottom

Bevel top

Spur bottom

Sector bottom
Posted Image
Sector top
Posted Image

Now lets lube the gearbox shell halves.

Posted Image

Next, we put the gears back in, starting with the spur gear. it goes in flat side down.

Posted Image

Now put the bevel and spur gear in. Check how the teeth line up and spin them, if they dont spin easily you may need to add or remove shims.

Posted Image

If they spin well and the teeth mesh together properly, then take out the bevel gear, and put the anti-reversla latch in its place.

The side with the spring over the axle faces down. The arm of the spring rests agaisnt the wallof the gearbox shell.

Posted Image
the axle goes in this hole.
Posted Image
Posted Image

Now put the bevel gear back in, making sure the arm of the anti reversal latch rests on the part of the bevel gear it must engage to keep it from spinning backwards.

Posted Image

Now we put the tappet plate/air nozzel back in. First, apply a bit of lube to the tapet plate where the air nzzel sits on it. This will keep the air nozzel from falling off while you put the tappet plate back in.

Posted Image

Now put the tappet plate with the air nozzel on it back into the gearbox. Rest part of the tappet plate spring on the gearbox shell where its supposed to go, then put the other side on the tappet plate, and put it in.
Posted Image

After its in, hold it down with your finger and push it back. It should move back and return foward smoothly.

Posted Image

Now if you havent already, put the cylinder head back in the cylinder, and insert the cylinder into the gearbox with the brass tube on the cylinder head sliding into the air nozzel.
Posted Image

End of Section five

#8 SpentBrass

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Posted 12 May 2007 - 06:25 PM

Section six

Now, we lube the piston and reinsert it into the cylinder.

Place the spring inside of the piston (obviously skip this step if your spring is attached to your piston)

Place the spring guide in the spring so that the tabs will go into their slots in the two halves of the gearbox. put the other half of the gearbox part of the way on

Now using the screwdriver again, push the spring guide/spring into the back of the gearbox, making sure the tab on ths spring guide line up with the holes in the gearbox shell.


When the spring guide is all the way in and lined up properly, set the other half of the gearbox most of the way down. You will have to line the gear axles and the anti reversal latch axle up to go into the bushings and the gearbox shell properly. A small screwdriver should work well for this.

When the axles for everything are lined up, the gearbox should be able to close fully. It should look like this

Now push on the tappet plate to make sure it still moves backward and returns smoothly.

Next, slide the metal plate over the top gearbox rail to hold it together.

At this point you should have your gearbox looking like this:

MMMMM metal bushings.......

Ok, now its time to put the screws back in the gearbox shell.


Now slip the motor mount back into the gearbox shell.


Put the screws in.


Now to re attach the safety.


Then place the trigger on the gearbox, and put the spring on it.


Now the selector switch transfer bar.

The right side of the gearbox should look like this:


Now we put the electircal assmebly back on the right side. There is a peg in the assembly which the trigger pivots on. This peg goes though these two holes which must line up.


After the electrical assembly is on, you will ahve to put that ball detent and spring back into it. The ball does into the hole first, then the spring, which should stick out a bit.


Now put the screws into the electrical assembly to hold it on.


Lastly, put the selector switch back nito place. It should have a peice which covers that tiny spring.



After those screws are in, the right side should be complete.


Now we will reattach the trigger switch to the left side of the gearbox. This should be fairly simple. There is a small palstic peg which sits in a hole in he side of the gearbox.



Now reattach the connectors to the motor. On my motor, black goes on top and red goes on bottom. Im not sure if they are all the same, but they should be.


Back to the left side, find this small grey metal peice.


It goes in like this:


The top of it should engage the switch as seen below. The other grey metal peice goes on as pictured.


Now put that metal plate back on.


Put the screws back into it


Next, put those small springs back onto their hooks. Once again, be careful.


Once the springs are on, you should be done reassembling the gearbox. I would reccomend hooking up a fusebox and battery to the gearbox and dry firing it on semi once or twice to make sure everything is functioning correctly. If there is a problem, send me a PM and il see if I can help.



#9 Guest_sniperjesus_*

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Posted 12 May 2007 - 07:08 PM

Great Guide :wink:

#10 Comrade_MP

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Posted 12 May 2007 - 08:01 PM

Got a love thinking up a disclaimer.

Pics were great, nice and big for easy viewing. Explainations greats, very nice work.

#11 SpentBrass

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Posted 12 May 2007 - 09:28 PM

Finally done!!!!!!

Wow that took a long time...

Thanks for the compliments, though I personally think your V3 guide was better, Comrade.

If anyone sees any screwups or typos, let me know about them.


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Posted 12 May 2007 - 10:33 PM

ever hear of thumbnails???

great guide though!

#13 sniperm82

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Posted 13 May 2007 - 04:43 AM

Did you happen to get into the hop up? When I got mine out, it looked pretty complicated because of all the small parts. I didn't go any further in fear of breaking something.

#14 AmigoOne

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Posted 13 May 2007 - 05:06 AM

My head exploded from the awesomeness

#15 SpentBrass

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Posted 13 May 2007 - 05:36 AM

Did you happen to get into the hop up?  When I got mine out, it looked pretty complicated because of all the small parts.  I didn't go any further in fear of breaking something.

Ive done my hopup before, its actually very very easy. I can go a guide on that aswell, maybe next weekend.

#16 Blink43va

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Posted 13 May 2007 - 04:04 PM

Damn dude!


I wish I would have had this when I first took apart my SOC 16...

Thankfully I have taken a few M14's apart and I am pretty much familiar with em!

-Blink :wink:

#17 sniperm82

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Posted 13 May 2007 - 04:17 PM

Did you happen to get into the hop up?  When I got mine out, it looked pretty complicated because of all the small parts.  I didn't go any further in fear of breaking something.

Ive done my hopup before, its actually very very easy. I can go a guide on that aswell, maybe next weekend.

Sweet, thanks. And good job on the guide.

#18 SpentBrass

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Posted 13 May 2007 - 04:37 PM

Hmm. some of the pictures are failing to load for me, is this happening to anyone else?

If it is, I may need to upload the pictures to a permanent imageshack account.....

#19 SYKO

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Posted 28 May 2007 - 11:21 PM

hey, thats from my camera

#20 lethal205

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Posted 17 June 2007 - 07:23 PM

Glad this was stickied, there aren't many Ver.7 guides out there.

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