Airsoft Gearboxes

If your M4 needs a revamp, a new gearbox is the easiest way to do it. The Delta Armory Complete Version 2 Gearbox for M4/AR-15 AEG is compatible with almost every M4/AR-15 AEG on the market and is well-equipped with reinforced parts straight out of the gate.

This is the same gearbox used in the Delta Armory CHARLIE™ line AEGs, boasting a quick change spring guide, 18:1 steel gears running on 8mm bushings, an SHS piston with a full steel tooth rack, an SHS reinforced tappet plate and a reinforced gearbox shell with radiused cylinder window corners.

The pre-installed spring will provide around 380 FPS when installed, so if you plan to use this gearbox for anything other than a semi-auto-locked DMR build you will need an M100, M105 or weaker spring to keep it within site limits. Thankfully, the quick change spring system makes spring swaps a breeze! Whether you are breathing new life into an old M4 AEG or you are building an AEG from scratch, this complete gearbox will save you loads of time and messing around!

If you have had a gearbox failure and you don't fancy opening it up, the CYMA Complete Version 2 Gearbox w/High Torque Motor & ETU is a pre-upgraded and pre-wired replacement which can be installed with minimal effort and no need to solder or open the gearbox shell. As always, we recommend you have some technical experience before installing a new gearbox, but when it comes to Airsoft upgrades this is about as easy as they get.

This gearbox set is designed for M4/AR-15 AEGs and has the correct nozzle length and selector plate for the task and is also pre-wired to a Deans connector so you can benefit from a lower resistance connector for increased electrical efficiency. Also included with the set is a CYMA high torque Neodymium magnet motor, providing a very snappy trigger response and the power to handle stronger springs than a standard motor.

The icing on the cake is the pre-installed MOSFET/ETU which prevents gearbox lock-up on semi-auto, provides further improvements to the trigger response and a boost to the rate of fire. If your M4 gearbox has issues or you want to freshen up an old M4 with a brand new and pre-upgraded gearbox this set would be a fantastic choice, avoiding the messing around and getting you back to shooting with minimal effort!

If you're looking for the cheapest and easiest way to convert your M4/AR-15 AEG to HPA, you just found it! The Ares Drop-in HPA Engine Conversion Set for M4/AR-15 V2 Gearbox is a complete set with a V2 gearbox shell, HPA engine and EFCS module all pre-built, saving you hassle sourcing the right parts while saving you a few quid as a bonus!

This HPA Engine Gearbox is designed as a drop-in replacement for standard M4/AR-15 AEG Version 2 gearboxes but it may need alignment and tuning to fit certain receivers and HOP-up units. To power the pre-installed EFCS, an 11.1V LiPo battery with an XT30 battery connector is required and the air line fitting is US spec, meaning it will only accept US-type air lines and won't work with EU-type lines. For those as yet uninitiated future HPA players; this set does not include an air line, regulator or air bottle and you will need these to get into the HPA game!

This is the semi/full auto version designed for non-ambidextrous M4/AR-15 AEG receivers and is equipped with a standard M4/AR-15 curved trigger, ideal for almost any build style. As with any internal upgrade, this engine will require expertise to install and some level of familiarity with M4/AR-15 AEG internals. If you're struggling, you can contact us or your local Airsoft tech for advice.

Whether you are upgrading your SMG-5 or repairing it, the CYMA CM.041G/CM.041H Complete Gearbox E-Edition High-Speed is a great excuse to do both at the same time! This gearbox is a Version 2, designed for CYMA CM.041 series SMG-5 AEGs but should fit most SMG-5 AEGs on the market (not SMG-5K) and also includes a high-speed motor of the long shaft variety.

As the heart of the CYMA E-Edition High-Speed Platinum AEG series, this gearbox is absolutely packed with upgraded parts. Highlights of the internals include the CYMA MOSFET/ETU system, steel high-speed 13:1 ratio gears, an aluminium silent piston head and cylinder head and a quick change spring system. Being a replacement original parts set, this gearbox is the exact setup found in the superb CM.041G and CM.041H AEGs, meaning if you have ever been envious of their performance you can now make your SMG-5 shoot just as nicely!

If you're looking to revamp your old SR25 why not take a walk on easy street and replace the whole gearbox? The CYMA CM.098 SR25 V2 Long Gearbox Set w/Motor is the exact gearbox used in their CM.098 SR25 series and should be compatible with Classic Army style SR25 AEGs which use the version 2 long gearbox (Classic Army, CYMA and A&K). This gearbox is well equipped, and includes a MOSFET/ETU prewired in, a quick change spring system, an M130 spring and also includes a high torque Neodymium magnet motor. Perfect to fix up an old big boy AR!

Ideal for reviving worn out RIFs or as a backup for a rainy day, this is a complete and assembled gearbox including motor, that is ready to drop into any compatible Version 2 accepting replica.

A pre-assembled, ready to use complete gearbox set designed for use in 6mm Airsoft BB replica M14 AEGs. With all the components assembled and in place, this gearbox is ready to be dropped into place in your M14 AEG, replacing any old and worn out gearboxes.

A complete V6 gearbox designed as a replacement for CYMA P90 AEGs to breathe new life into your weapon.

Redesigned for maximum compatibility with a wide variety of brands, the RetroArms CNC QSC Gearbox V2 is ideal for technical Airsofters working on a high-performance build which needs to last a lifetime. The set includes a Version 2 gearbox shell, carbon steel screws and a steel ball bearing spring guide and is ideally used for extremely high ROF or FPS builds. 

The shell itself is precision machined using CNC technology from the best aluminium around; 7075 T651, an ultra-hard alloy with similar strength properties to steel, boasting an ultimate tensile strength of 590 MPa compared to construction steel's 390 MPa. The quality of the machining simply cannot be overstated; every surface is flawlessly smooth and finished to perfection. 

Not content with making an absolutely beautiful gearbox from the finest materials around, the team at RetroArms has also put a lot of thought into the design aspect, improving on the original Tokyo Marui V2 gearbox in several areas. The piston tracks and selector plate rails have been redesigned for wider compatibility, the front of the gearbox is enlarged in every dimension to improve strength, "glue pockets" have been added around each bearing hole so they can be glued in and wider internal wiring routes for heavy gauge wiring, along with much, much more. If you're the techy type seeking a slick gearbox shell to start your build, the RetroArms CNC QSC Gearbox V2 is exactly that!

If you're working on a high-speed or high FPS build, the Delta Armory Version 2 CNC 8mm QSC Gearbox Shell will save you a lot of heartache in the long run! This ultra-strong version 2 gearbox shell is CNC machined from the best aluminium around, known as 7075 T651. This means if you're running a super strong spring or going for a dual-sector gear build, this gearbox shell has what it takes to keep running in the long term, being considerably stronger than standard alloy gearbox shells.

The QSC Gearbox shell also features radiused cylinder window corners to better distribute force and is pre-cut for Gate TITAN/ASTER, Perun Hybrid or Delta Armory ETU MOSFET systems, meaning no need to get the Dremel out to add advanced functionality. The bearing ports are 8mm in diameter, making this the perfect host for Bolster Armouries EZO Ball Bearing Bushings. If you're reaching for the stars when it comes to performance and want your build to last more than a few bursts, the Delta Armory Version 2 CNC 8mm QSC Gearbox Shell is what you need!

The Spenca CORE™ V2 Gearbox Shell provides 8mm bushings, radiused cylinder windows to help prevent cracks, and quick release spring functionality. Perfect for starting your ultimate gearbox build! 

Building a gearbox from scratch? You'll need a shell to get started! The ARCTURUS Version 3 Alloy Gearbox Shell is a reinforced design with a radiused cylinder window, additional material surrounding the cylinder for extra strength and 8mm bearing holes. The rear of the gearbox is also cut for a quick change spring guide. 

The version 3 shell is common to AK, AUG, AR36 and SMG-5K AEGs (not the regular SMG-5, though) so if you need a gearbox shell for any of these platforms this one will be compatible in most cases. 

If your AK AEG needs a revamp, the S&T Complete V3 Gearbox w/ Micro Switch for AK AEGs is the easiest way to give it a new lease of life. This is a complete version 3 gearbox fitted with an AK nozzle, selector plate and top cover retention latch, though if you run an AR36, SG55x or SMG-5K you can swap these parts out for your original bits and use this gearbox in your replicas too. 

Inside, we have an impressive set of internal parts including 18:1 CNC steel gears, 8mm bushings, a steel quick change spring guide, a polymer piston with a full steel tooth rack, a CNC steel cylinder and CNC aluminium piston and cylinder heads. The wiring is low resistance and fitted with a mini-Tamiya connector, wired to suit front-wired and top-wired AK AEGs. The trigger is the "micro-switch" type, improving trigger response and longevity when compared to conventional copper trigger contacts. 

Complete gearboxes are the easiest way to fix gearbox issues for those who are less technically confident or those who don't have time to fiddle with the internal parts of their pride and joy. Whether you've got an AK AEG to fix, are working on a custom build or want a gearbox to learn the technical aspects of the hobby, the S&T Complete V3 Gearbox w/ Micro Switch for AK AEGs is a fine choice!

If you are looking for a high end gearbox shell to start your ultimate AEG build, stop looking, you found the best there is! The Gate EON gearbox shell is CNC machined from 7075 aluminium for a strong and lightweight gearbox with a plethora of small enhancements that make this gearbox a dream to put together.

The cylinder window is radiused on all corners and the shell has some significant reinforcements at the front end, and along the top spine. The internal wire routing has been redesigned for ease of installation, and the shell is perforated with several inspection windows so you can set your angle of engagement, adjust your pre-cocking settings and shim your gears perfectly. Is this the ultimate Airsoft gearbox? Well, it will be, once you've built it!

If you are looking for a high end gearbox shell to start your ultimate AEG build, stop looking, you found the best there is! The Gate EON gearbox shell is CNC machined from 7075 aluminium for a strong and lightweight gearbox with a plethora of small enhancements that make this gearbox a dream to put together.

The cylinder window is radiused on all corners and the shell has some significant reinforcements at the front end, and along the top spine. The internal wire routing has been redesigned for ease of installation, and the shell is perforated with several inspection windows so you can set your angle of engagement, adjust your pre-cocking settings and shim your gears perfectly. Is this the ultimate Airsoft gearbox? Well, it will be, once you've built it!

If you want a 'FET on your AK but don't fancy chopping up your gearbox shell, the ARCTURUS Version 3 Gearbox Shell; MOSFET Ready will sort you out! This alloy V3 gearbox shell includes 8mm steel bushings pre-installed and is designed to accept the standard V3 trigger switch, a Perun Hybrid V3 MOSFET or a Gate TITAN V3 MOSFET, meaning no need to get the Dremel out!

Being a V3 shell, this is compatible with most AK, AUG, AR36 and SMG-5K AEGs but doesn't include any internals other than the bushings. The rear of the shell is cut for a quick change spring guide and we recommend sourcing one from ARCTURUS to guarantee compatibility. Whether you aren't a fan of using power tools or you simply CBA, the ARCTURUS Version 3 Gearbox Shell; MOSFET Ready will help bring your AK up to speed with the most advanced builds on the field!

If you are worried about trapping your wiring when inserting a magazine or reinstalling your MCX handguard, Laylax has once again come up with a solution! The Wire Guard for MCX AEG is designed to mount to the gearbox shell and keep your wires well out of the way of any snags or potential damage from inserting magazines or removing/reinstalling the handguard. If you want to get ahead of one of the known problem areas of the MCX and save yourself some hassle down the line this affordable upgrade could save you time and money!