Spring Info

Systema measures their spring strength with.25s though. Stock TM is around 85 Meters per second or 3.28*85= 278.8 M/s
M90 is around 300.
The % springs are based on TM standard with .20s I believe so the PDI 120 is 278.8+ (..2)278.8= 335FPS

Basic Marui Gearbox Information

In certain electric guns there are different types of gearboxes and common guns that use those gearboxes. There are different types of gearbox sets such as the TOP, STAR, and Tokyo Marui. The most used is the Tokyo Marui set, which is what this guide is on.

Geaboxes in General
Gearboxes aren’t exactly a simple subject. Some tend to be weaker than others. Some tend to have more problems than others. You need to know the risks of getting a gun using that gearbox version before you get it. For example, what if you get a gun with a get a gun with no upgrade parts available? What if the gearbox shell is extremely weak? You need to know before you buy that gun.
One thing to remember is that gearbox versions shouldn’t completely decide your gun. Every gearbox has its good and bad. If you really want the gun but the gearbox version for it isn’t the best, go ahead and buy it as long as you know the risks. This is here for reference on what to look out for and what you should be careful with to avoid any long term problem - not to decide your gun solely on the gearbox version.

Quick Overview of Gearbox Internals
Essentially, the gearbox is made of different parts. Here, I will briefly explain each part and how they correspond with each other. Pictures are not in order, so be sure to look at the picture number.
The pictures may be of low quality due to the JPEG file type. Other file types used would have resulted in extremely large file sizes.

IPB Image

First look at picture one (1). This is a motor inside its motor cage. Not all motor cages look like that, but they hold the motor in place. This particular motor cage goes to a M1A1 Thompson. On each motor, there is a gear at the top called the pinion gear. Motors are magnetic so be sure to treat them accordingly. There are three types of motors with different lengths. These are short, medium, and long.

Now look at picture two (2). This is a Version 6 gearbox for a M1A1 Thompson. The Version 6 M1A1 Thompson gearbox was chosen because of its user friendliness This is the box that makes your gun shoot. There are different names for this box. More commonly, they are called “gearboxes.” Sometimes, you may find the usage of “mechbox” or “mechabox.” Each gearbox version is unique in it’s own way.

If you take apart the gearbox, you get to picture three (3). A gearbox consists of a few parts. This includes the spring guide, spring, piston, cylinder, cylinder head, nozzle, tappet plate, gears, bushings, shims and anti-reversal latch. These will be explained later. In certain gearbox versions such as Version 2 and Version 3, the trigger assembly and wiring would be in the gearbox. In the Version 6 gearbox, it is an external wiring system, which you can define as the black box with the trigger in picture two (2).

The piston which is picture four (4) is one of the parts that compresses the spring. The piston head, which is attached to the top of the piston, is one of the main air compression components. The piston has teeth that the sector gear - explained later - grabs onto. When the sector gear finally passes its last tooth, the piston is then released. The piston head will then compress the air with the O-Ring that is around it. There are two common types of pistons. One is polycarbonate which is a strong plastic. The other is aluminum. Polycarbonate pistons are used for weak to medium power and/or high rate of fire set-ups. The aluminum piston is usually for high FPS set-ups. It has been said the aluminum piston is a gearbox shell killer due to the material it’s made of.

The gears of the guns in picture five (5) are one of the main parts that compress the spring. In the picture, the gear on top is the sector gear. The sector gear is connected to the spur gear, tappet plate, and the piston. The sector gear is the gear that usually wears down the fastest. It pulls back the piston with its teeth, compressing the spring. It also pulls back the tappet plate with the little rod that is sticking up - which is explained later. The sector gear also moves the cut-off lever for you to achieve semi-automatic in most gearbox versions. Tokyo Marui uses an aluminum sector gear in their guns unlike some other airsoft gun manufacturers so the sector gear may wear down quicker.
The second gear is the bevel gear. The bevel gear is connected to the anti-reversal latch, the pinion gear on the motor, and the spur gear. When the motor spins, it makes the bevel gear spin. This causes the spur gear to spin. If a full cycle has not been completed, the anti-reversal latch grabs onto the notches in the bevel gear. The bevel gear usually doesn’t wear down as much as the sector gear. However, a bad motor adjustment will make it wear down much faster.
The final gear is the spur gear. The spur gear is in the middle and connects the sector gear and the bevel gear. The sector gear wears down the least of the three gears, but doesn’t make it invincible.
For all these gears, bad shimming will cause them to wear down much faster. Be sure to shim all these gears!

In the sixth picture (6), there shows two tappet plates. The one above goes to a Version 6 gearbox. The one below it goes to a Version 2 gearbox. The tappet plate is connected to the nozzle - which will be explained later - so it can load a BB. Tappet plates are usually plastic.

The anti-reversal latches in picture seven (7) are essential to prevent your gearbox from unwinding. If you are shooting, and the piston only goes halfway back, the anti-reversal latch is there to stop it from unwinding. Instead, it grabs onto a notch in the bevel gear and keeps the bevel gear from reversing, therefore doing the same for the other parts. If your anti-reversal latch is missing or malfunctioning, do not shoot your gun. It could cause severe damage.

In picture number eight (8), there are cylinders. This is one of the main components of compressing the air. When the piston and piston head enter, the cylinder helps compress the air. There are different cylinders with different sized holes for depending on your barrel length. Although you can use any barrel length with any cylinder, using a certain cylinder will increase your performance.

In picture number nine (9), there are cylinder heads. These are connected to the cylinder, nozzle, and is constantly getting hit by the piston head. When the air is compressed by the cylinder/piston head, the cylinder head offers the compressed air an exit where it then blows the BB out chamber through the attached nozzle.

The selector plate in picture ten (10) is only found in select guns and are different for most models. This particular selector plate is for the M4/M16. It is the thing that determines if your firing mode is safe, semi, or automatic. The selector plate is connected to a cut off lever to make semi-automatic work.

The bushings of a gun depicted in picture (11) are what the axles of the gears spin on. There are two common materials bushings are created from. These are nylon and metal. Nylon plastic bushings are usually made for stock or weak guns. Metal bushings are for guns when they have mid to high range FPS. Metal bushings give more durably than the nylon ones. The bushing sizes are usually 6mm. However, there are different sizes of bushings as well such as 7mm and 8mm bushings. These give the gun less stress due to their larger sizes. However, you will need a 7mm gearbox to use 7mm bushings. The same goes for 8mm.
In the picture, two types of bushings are shown. The completely circular ones are normal bushings and are used in all common gearbox versions. The oval ones are only used twice in Version 6 gearboxes. The oval bushings are for the spur gear in the Version 6 gearboxes.

Picture number twelve (12) shows spring guides. The guide on the left is a plastic spring guide found in most stock Tokyo Marui guns. The one of the right is a metal spring guide with bearings. The spring guide is the thing that sits at the end of the piston rails at the back of the gearbox. The spring stays in place because of it so it doesn’t move around and fly all over the place.
The one on the right is more efficient than the one on the left. The metal spring guide with bearings allows the spring to maneuver around so the spring will not twist up. The plastic spring guide without bearings does not do this. A spring guide with bearings may increase your FPS; the FPS usually isn’t noticeable.

The shims in picture thirteen (13) are “spacers” for your gears. Without these, your gears may be spinning against what it shouldn’t be such as the gearbox shell. Although they are not required in a gearbox, it is still HIGHLY recommended you put a good amount in your gearbox correctly. A good shim job could result in higher rate of fire, slower wear of parts, and longer battery life. However, a bad shim or no shims at all would restrict your gun’s rate of fire, wear down parts faster, have shorter battery life, locking up gearboxes, and many more problems.

Remember, this is just a brief explanation. If you need more information, you should look into specifics for your gun and brand. Remember, pictures and text is great, but hands-on and experience is the best.

Compatibility Between Successful Gearbox Versions
This chart covers the four more successful versions of the gearboxes. These are the V2, V3, V6, and V7.
IPB Image

[V#] - The “#” will be replaced with a number. Whatever number is there, that is what the gearbox version part it is compatible with.
[GS] - This means it’s gun specific where the part is completely dependant of the gun model.
[ST] - This is the standard or the most common. Version 2 and Version 3 compatible parts are standard.
[2S] - This is the second standard. These parts will only fit Version 6 and Version 7.
[NA] - Not Applicable.

[SH] - Gearbox Shell: The gearbox shell is version specific. So a Version 2 gearbox can’t fit in a gun made for Version 7.
[GR] - Gears: The gears for Version 2 and Version 3 are compatible. However, the Version 6 and Version 7 gears have smaller spur gears.
[PS] - Piston/Piston Head: The piston and piston head are compatible for all four versions.
[TP] - Tappet Plate: The tappet plates are all version specific. The Version 2 and Version 3 look similar, while Version 6 and Version 7 look similar.
[AR] - Anti-Reversal Latches: Version 2 and Version 3 use the same standard anti-reversal latch. The Version 6 and Version 7 use different anti-reversal latches, which are reversed.
[SG] - Spring Guide: Spring guides are a tricky thing. Version 2 uses Version 2 spring guides. Version 3 can use Version 2 spring guides (not recommended) and can use their V3 spring guide with a fatter end. Version 6 gearboxes use a Version 2 spring guide. Version 7 gearboxes have their own M14 spring guide made for them.
[NZ] - Nozzle: Nozzles are gun specific because the hop-up chamber is placed differently on all of them.
[MT] - Motor: Motors are gun specific. Although many, if not all, motors for the Version 3 are short, there could be exceptions. For example, the P90 and M1A1 Thompson which use the Version 6 gearbox use different motors. The P90 uses a long motor while the Thompson uses a short.
[CY] - Cylinder: Version 2, Version 3 and Version 6 uses a gun specific cylinder but are all the same size. Depending on your barrel length, you want one with different sizes and amounts of holes in it. Version 7 cylinders are 2mm longer than the standard cylinder size so standard cylinders will not work.
[BS] - Bushings/Shims: Bushings are standard for Version 2, Version 7,and Version 3. However, the Version 6 bushings use two special oval shaped bushings. The other four bushings on the Version 6 gearbox are compatible with Version 2, Version 3, and Version 7. Shims are compatible with all gearbox versions.
[WS] - Wiring/Trigger/Selector Plate: Wiring and triggers are gun specific. The gun could be wired to the back or front. Different model triggers cant fit in other guns and so on . Selector plates are gun specific as well since all selector switches aren’t the same. Some guns don’t even have a selector plate.
[MC] - Motor Cage: Motor cages are gun specific for Version 7, Version 3, and Version 6. For example, the AK-47, G36C, and the MP5K all use Version 3 gearboxes. Well, an AK-47 can’t use a G36C motor cage, and vise-versa. A MP5K doesn’t even use a motor cage. Version 2 gearboxes do not use a motor cage because motors are put in the pistol grip only. There isn’t even a place to mount a motor cage if people wanted to make one.

Version 1 Gearboxes
The Version 1 Gearbox was Marui’s first gearbox that was developed hence the number “Version 1.” It was one of the, if not THE, first gearbox designs for an electric gun.
The Version 1 gearbox is best known as used in the Marui FAMAS, which is also Marui’s first electric gun.
The main features for the Version 1 gearbox is a high rate of fire due to it’s design. It is also pretty durable in comparison to a Version 2 or a Version 5. The motor is inside the gearbox for this model.
However, there are certainly downfalls. Being this the first of Marui’s line, there are a lack of aftermarket parts available. If you’re planning to upgrade this gun to a higher FPS, there are barely any parts out there for you to reinforce your parts with. This also means if any of your parts wear down or break, there are certain parts you cannot replace either.
Another gun using the Version 1 gearbox is the Academy L85. It was the first L85 AEG out and appears to be the only L85 with a Version 1 gearbox.
Overall, you should not buy a gun with this gearbox if you plan to upgrade it. If you plan to leave the gun stock, there may be some logic in buying this gun.

Verison 2 Gearbox
The Version 2 gearbox was the first gearbox to be widely used. Version 1, which was used in the FAMAS was not widely used like the Version 2.
There are actually many guns that use the Version 2 gearbox; there are also many that aren’t even made by Marui.
Common guns that use the Version 2 gearbox are the Tokyo Marui M4A1, Tokyo Marui M4 S-System, Tokyo Marui M16A1, Tokyo Marui M16VN, Tokyo Marui M16A2, Tokyo Marui M733C, Tokyo Marui SR-16, Tokyo Marui XM177E2, Tokyo Marui CAR-15, Tokyo Marui MP5J, Tokyo Marui MP5SD5, Tokyo Marui MP5SD6, Tokyo Marui MP5A4, Tokyo Marui MP5A5, Tokyo Marui MP5 RAS, Tokyo Marui MC51, Tokyo Marui G3SAS, Classic Army M15A4 SPC, Classic Army M15A4 SPR, Classic Army M15A4 CQB, Classic Army M15A4 Carbine, Classic Army M15A4 Tactical Carbine, Classic Army M15A4 RIS, Classic Army M15A4 RIS Carbine, Classic Army M15A4 Compact, Classic Army M15A4 Compact SEAL, Classic Army CA33, Classic Army MP5SD2, Classic Army MP5SD3, Classic Army MP5SD5, Classic Army MP5SD6, Classic Army MP5A2, Classic Army MP5A3, Classic Army MP5A4, Classic Army MP5A5, Classic Army M15A2, Classic Army M15 XM177E2, Classic Army M15A2 Carbine, Classic Army M15A2 Tactical Carbine, Classic Army SCAR, ICS MP5A2, ICS MP5A3, ICS MP5A4, ICS MP5A5, ICS MP5SD2, ICS MP5SD3, ICS MP5SD5, ICS MP5SD6, and their respective clones.
As you can see, the Version 2 gearbox is widely used by many brands and their clones which even adds more to the list. However, being that they are used by many models - it still isn’t the best.
The main reason why the Version 2 gearbox isn’t the best is because of its overall build. The gearbox’s main weak spot would be the front. If a spring becomes too powerful or the gearbox cant take it anymore, the front usually just cracks and thus making you have to buy a new gearbox. Nowadays, some manufacturers use reinforced gearboxes to fix these problems, generally adding extra thickness where there can be extra thickness. This helps a lot on the gearbox’s reliability.
Due to the usage as shown above, there are MANY aftermarket parts made for these gearboxes. Almost every part used in these gearboxes are replaceable with better, aftermarket parts, making a Version 2 gearbox a good upgrade platform.
A downfall to the Version 2 gearbox is where the motor is placed. Motors for the Version 2 gearbox are generally in the pistol grip of the guns instead of the motor cage used in other versions. If you put it in too much the gearbox will not work. If it is not significantly in enough, the motor and the gearbox create a screeching sound that wears down the gearbox/gears and the pinion gear.
There are other variants to the Version 2 gearbox. For instance, the ICS M4/M16s have a modular gearbox design instead of the common one piece Version 2 gearbox. The JLS F2000 also uses a modified Version 2 gearbox.
Overall, the Version 2 gearbox is a decent performer and is good for upgrading. There are better, but certainly not the worst gearbox version.

Verison 3 Gearbox
The Version 3 gearbox is very much like the Version 2 gearbox in shape but performs differently.
It is used in many guns, but not as much as Version 2.
The Version 3 gearbox was one of the first gearboxes to have a nearly flawless in design.
Common guns that use the Version 3 gearbox are the Classic Army AUGA1, Classic Army AUGA2, Classic Army CA36C, Classic Army CA36K, Classic Army CA36E, Classic Army SLR-105 A1, Classic Army SLR-105 Steel, Classic Army SLR-105 Compact, Tokyo Marui AK-47, Tokyo Marui AK-47S, Tokyo Marui AK-47 Spetsnaz, Tokyo Marui AK-47 Beta Spetsnaz, Tokyo Marui G36C, Tokyo Marui SIG SG 552-2, Tokyo Marui MP5K, Tokyo Marui AUG Civilian, Tokyo Marui AUG Military, AGM MP40 and their respective clones.
Although not as widely used as the Version 2 gearbox, there are still many aftermarket parts available for it. Almost every part, like the Version 2, is replaceable or upgradeable. Some parts are interchangeable between Version 2 and Version 3.
The Version 3 gearbox does not suffer the same problems as the Version 2. It does not have a weak front end, and is not as prone to cracking as much. The Version 3 gearbox is arguably one of the best gearbox versions created.
Another good feature of the Version 3 gearbox is that most of the guns that use this gearbox version have a motor cage to hold the motor. This would contribute to better reliability so you don’t accidentally misadjust the motor so it would screech and wear like on a Version 2 gearbox. An exception to this would be the MP5K, where there is no space for a motor cage.
However, the motor’s wires are soldered onto the motor. If you ever want to upgrade or replace your motor, you may have to go through a lot of trouble to do so.
Overall, the Version 3 gearbox is perfect for upgrading. They are extremely durable, have many parts available, and are easy to work on.

Verison 4 Gearbox
The Version 4 gearbox is a unique and strong gearbox. It has a split gearbox design - also called a modular gearbox. The Version 4 gearbox is used only by the PSG-1 at the moment.
The Version 4 gearbox’s split gearbox design doesn’t make it any weaker. The Version 4 gearbox is actually a pretty strong design and is probably in the higher levels of gearbox versions.
Inside the gearbox shell is something different. This is a unique gearbox design, which means certain parts will not work in this gun. You need to buy specific gears, cylinders, cylinder heads, and springs for this gun. The springs and gears are one of the more common parts inside a Version 4 gearbox. However, the cylinder, cylinder head, and other parts inside are hard to find.
The gearbox can only fire in semi-automatic being that the PSG-1 is more of a marksman rifle than an assault weapon. The spring is pre-compressed in this gearbox version so the gun doesn’t have to go through a full cycle to shoot. Instead, once you pull the trigger, the air is immediately compressed. It also has a feature where you can release the spring after you’re done since dry firing to release will not work like in other AEGs.
Overall, the Version 4 gearbox is good for shell durability. Inside the shell, the parts are pretty decent but could be hard to find.

Verison 5 Gearbox
Long skinny gearbox anybody? Let me first state that the gearbox is mainly plastic. Is that a turndown? What about little to no aftermarket support? What about if it’s only used by the Tokyo Marui Uzi?
The gearbox is a plastic polycarbonate box. Being that the Tokyo Marui Uzi doesn’t have THAT high of a FPS, it’s probably okay for that gun. However, it’s still plastic, so it will break faster than most other metal gearbox versions.
Aftermarket support is little to nothing for the Version 5 gearbox. Where was the last place you saw a Version 5 tappet plate? How about a Version 5 cylinder head? What about a polycarbonate plastic gearbox shell? If you search hard, you might not even find one. If you do find one, it’s most likely in Hong Kong. So, what are you going to when that part finally wears out? What if it breaks? Well, there isn’t much you can do until luck strikes you - but what are the chances of that happening? Or, maybe you want to upgrade your UZI because you think the FPS is way too low. However, the polycarbonate gearbox shell is still blocking your way. You’re not going to find a metal gearbox shell. Any high power upgrade will kill the gearbox shell.
Now, there is some minor goodies that come with this gearbox. First, the “real-shock” system is in this gearbox version which makes the Uzi so much fun! It also has been said it uses a metal tappet plate. Tappet plates usually don’t die, but it’s probably one of the first metal ones.
Overall, there is almost no reason to get an Uzi/Version 5 gearbox except if you REALLY need/want an Uzi, just love the “real-shock” system, or think that 2+2=22.

Verison 6 Gearbox
The Version 6 gearbox is one of the best gearbox versions to ever appear in the market. It’s durable, easy to disassemble out of the gun, easy to reassemble, and more.
The Version 6 gearbox was originally made for the M1A1 Thompson. Later in Marui’s development, they created the P90 using the Version 6 gearbox. The only difference was the way the motor was mounted, which was to the side unlike the M1A1 Thompson which was in a pistol grip.
Most parts are compatible with the Version 2 gearbox. The main parts that are not are the bushings, the cylinder head, the tappet plate, spur gear, and the anti-reversal latch. Out of all these parts, the cylinder head and the spur gear are the hardest one to find. Two of the bushings on the Version 6 gearbox are oval shaped and can be found at many airsoft retailers. The spur gear is smaller because space is limited in the Version 6 gearbox.
The Version 6 gearbox was also one of, if not the, first gearboxes to be modified to allow a bolt mod. This mod was done for the M1A1 Thompson by Lifehost.
Overall, the Version 6 gearbox is a durable gearbox good for upgrading or leaving stock since it’s durable and easy to work on.
On a side note; the Version 6 gearbox is more prone to have their tappet plates break when opening the gearbox. Make sure that the tappet plate is fully released before opening the gun.

Verison 7 Gearbox
The Version 7 has a nice durable shell and limited unique parts. Most parts are compatible with a Version 2 gearbox.
The Version 7 gearbox was specially designed for Tokyo Marui’s M14. The M14 is a nice Designated Marksmen Rifle, but needs to be upgraded to reach it’s full potential as one. The M14 has been known for extremely hard disassembly - which means you get a headache trying to get to the gearbox. You have to take the body off, take the things surrounding the gearbox, remove the motor and it’s cage, and remove the wiring.
The Version 7 gearbox has a smaller spur gear like the Version 6. Finding a replacement may be a bit hard. Most other main parts are available for replacement.
The Version 7 gearbox overall is a pretty good shell externally and there are no extreme loss of aftermarket parts. If you want a M14, don’t let this gearbox design stop you!

Version 8 Gearbox
The Version 8 gearbox is only used in the Type 89. It’s a decent design; there are better.
It is pretty much a Version 2 gearbox with a burst function. Unlike the SIG series from Marui that had burst functions, the Version 8 is mechanical instead of electrical. This should mean that there will be less problems with bursts compared to the SIG.
Most parts that work with the Version 2 gearbox should work with the Version 8 with a few exceptions. However, the special parts such as the selector switches and the mechanical burst parts will be almost impossible to find at the moment.
Overall, the Version 8 gearbox is a decent choice. The main purpose for it was a mechanical burst - which it succeeded in. If you want a Type 89, go for it.

Version ? Gearbox
Recently announced, a TM AK will have a gearbox with an actual recoil system. Whether it be a modified Version 3 or not, it will most likely be a new gearbox version. (October 8th, 2007)

Remember, gearbox version isn’t the whole part of the reliability of a gun. There are many other factors that would cause the gun to increase or decrease in reliability.
However, the gearbox shell is one of the larger factors.

So go out and get the gun you want, knowing the risks and benefits of getting a gun with that gearbox version.

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