Tips for Working on Gearboxes
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  1. #1
    Doin' barrel rolls! Fox's Avatar
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    May 2011
    My Arwing but mostly The Great Fox mothership.

    Post Tips for Working on Gearboxes


    *DISCLAIMER*: I do not recommend; encourage; or suggest disassembling any airsoft weapon or gearbox. Gearboxes can be quite complicated and difficult to work on. Do so at your own risk. These are only some basic tips for gearbox-virgins (pardon the expression). Keep in mind almost all airsoft retailers will void any warranty or guarantee if you disassemble your weapon or gearbox in any way.

    Opening the gearbox of any AEG for the first time is usually, and rightfully should be, a daunting task. Whether you desire to open your gearbox just for fun; to see what it looks like; to determine the quality of the components; to clean and re-lube it; to upgrade or repair it, you must first know what you are getting into. Before you do anything, figure out what version of gearbox you have. You should be able to find this out by looking at your gun's manual if it came with one, or you can do a Google search to see what version of gearbox your type of weapon (M4 or M16, M14, G36, etc.) uses. If you would like more information on gearbox versions, check out Marsden's article here. For more information on the names and terminology of gearbox components, check out his other article here.

    Personally, I always disassemble my entire airsoft weapon and its gearbox shortly after obtaining it. I do this to clean out the crappy factory grease inside the gearbox, thoroughly clean the inner barrel, and re-lube/clean any other parts that require it. Some players will frown on me for doing this, as they follow a rule of only taking apart the gearbox if it needs repair or upgrade. That is probably a safe way to go, especially for those of you who are new to the sport, and those of you who are not confident in your ability to put relatively complicated machines with very tiny pieces back together. It is a matter of personal opinion and habit whether you open a gearbox before it needs repair, but once again, take a gearbox apart at your own risk.

    When you first take ownership of an airsoft weapon, it is important to first inspect its exterior and test fire your weapon to note how it is performing before disassembling any parts of it. (It is important to put at least 500 rounds through a brand new AEG in order to accurately judge it's stock performance). Prior inspection is important to do in order to know if you have messed up somewhere along the line of reassembly if your weapon doesn't work correctly when it's back together. Before you go ripping your new toy apart, Google search something along the lines of "gun name disassembly" or "gun name breakdown guide". If you find a website that isn't an online retail store, it might provide you with a step-by-step guide and possibly step-by-step pictures. Another really great way to get help with disassembly is to type the above suggestions into YouTube, where there are hundreds of great disassembly and reassembly videos. Try to find a video that isn't done by a little kid. I'm not saying it is impossible for a younger person to have lots of knowledge about gearbox maintenance, but your chances of finding a reliable video are going to be higher with an adult with lots of experience. Airsoft GI has a few quality videos on YouTube for airsoft gun maintenance. Also, is a wonderful site for videos of a select few of the more popular airsoft weapons.'s videos usually include a break-down AND re-assembly.

    Once you have your help guide or video ready, make sure you have all the appropriate tools you will need to disassemble and reassemble your weapon. The videos and guides usually have a bit at the beginning letting you know what you will need. For most AEG's, this will probably include a set of metric or english allen-wrenches, a phillips screwdriver, a regular screwdriver, a small phillips screwdriver, a small regular screwdriver, needle-nose pliers, and possibly some star-head screwdrivers and a small hammer.

    Disassembly of the body of an airsoft weapon is the easiest and most straightforward portion. The gearbox is where things get more challenging and risky. There are many tiny components in an AEG gearbox, all of which are essential to its proper function (that's why they're there in the first place). Lots of these small pieces are in front of a spring or loosely set in the gearbox. It is imperative that you disassemble your gearbox VERY slowly while over a large, hard surface such as a counter or table in case a piece goes flying or drops out and starts rolling away. Never disassemble your gearbox while sitting on a couch, lazy-boy, or any other plush seat with lots of small places to lose tiny parts in. It is also a good idea to disassemble in a non-carpeted area, as it is easier to lose tiny pieces in carpet. The best spot to have your gearbox when opening it is inside a shoebox.

    A couple specific tips when opening the gearbox:
    1. The spring that powers the piston will possibly explode out upon opening the gearbox. This may be unavoidable, but try to cup one hand around the rear of the gearbox and very slowly open it starting with the rear. It will also help to insert a skinny screw driver into the hole in the rear of the gearbox. You will push it in until it can't go any further, then apply pressure with it against the piston which will allow you to slowly release the spring when opening the gearbox.
    2. The trigger may decide to pop out, but it shouldn't go very far. The small, shiny anti-reversal latch will likely do the same. Other small parts and springs may do this also, so remember to open slowly and carefully over a large, flat surface.

    Once you have your gearbox open, if this is the first time opening it it would be wise to clean out all the crappy, clumpy factory grease and basically wipe down everything within the gearbox. Apply a small amount of fresh, high quality grease to these specific parts: Around the o-ring of the piston, the rails that the piston glides along, and a very small amount to the points of the gears where they meet the body of the gearbox. You also want to apply a small amount of spray lubricant around the piston and on the gears. If you desire, you may also apply lubricant to any other moving parts. You can buy airsoft grease and lube at online retail stores. It is important to only use grease and lube designed for airsoft guns. This is because real-steal firearm lubricants and other lubricants such as WD-40 can damage the plastic pieces in your gearbox.

    At this point, you are ready to reassemble your gearbox and weapon unless you have upgrades or repairs to do. Repairs and upgrades should be done before greasing and lubing the gearbox. Utilize any videos and guides you can find when reassembling your gearbox and weapon. Reassembly will be much more difficult than disassembly. A few things you will definitely have trouble with upon reassembling an AEG gearbox are the anti-reversal latch and the spring.

    A couple specific tips for gearbox reassembly:
    1. The anti-reversal latch will be the bane of your existence. You will HATE it. It will rarely stay in place, and it will keep popping out. It will also probably pop out the gear it sits against. In order to maintain your sanity, try to be patient as you will probably have to pull one side of the gearbox body off, replace the anti-reversal latch, and try putting the body back together again and again. It will help to get a small screwdriver and apply pressure on the anti-reversal latch from outside the rear of the gearbox (or through the hole for the motor) while placing the other half of the body back on. It might take you 2 minutes to get it right, but it also might take you an hour.
    2. The spring is going to be compressed, so it will want to explode itself and the piston out of place. Make sure the piston is sitting on its rails, and the spring is set in its notch at the rear of the gearbox. If the spring keeps giving you trouble, apply pressure on it with your fingers through the open spaces in the opposite half of the gearbox body while you place the the other half back on.
    3. The combination of trying to keep the spring and anti-reversal latch in place at the same time can be extremely difficult while using each hand to deal with each problem AND trying to put the body back together simultaneously. Just keep at it, try and try again if you need to, and maintain patience. Gearboxes are not meant to be taken apart by those with little patience. Have another person help you if you need an extra hand.

    That about wraps it up. If you have any questions or comments, post them on this thread and I will do my best to help. Remember the keys to gearbox work are patience, trial and error, prior planning and research, and use of videos and guides. If you want someone experienced to work on your gearbox for you, I can do so for a small fee. Just shoot me a Personal Message and I will see what I can do.

    Here is the first part in a series of videos that are a great visual guide for removing and operating on a Version 2 gearbox (The gearbox version used most commonly in M4, M16, MP5, G3). The other videos in the series should have links on the right side of the screen. [ame][/ame]

    Here is a Version 2 guide from another airsoft forum:
    Last edited by Fox; 04-17-2012 at 08:43 PM.

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