The mag well is held in by a straight through pin bolt. When you undo the nut the bolt can be retracted from the opposite side and the mag well then swivels away from the main body pivoting on the front lugs then away from the body.
With the middle bolt removed, you need to carefully detach the power connector hidden next to the hop unit (under the mag well hinge area). It’s a standard battery connector, so just unplug it and free the wires so that they aren’t wrapped around anything.
Before you try to remove the gearbox fold the stock back and remove the bolt that you will find in the rear of the main hinge. This bolt secures the hinge to the gearbox itself. To unscrew the bolt you’ll need the 3mm Allen key.
Now with the last bolt removed carefully swing the gearbox away from the main frame. Don’t force anything as there is not a great deal of room between the hopup unit and the front of the gearbox. The inner barrel is actually sprung against the front of the rifle meaning that as you swing the gearbox out the barrel and hopup unit move forward, and then spring back in place. This is worth bearing in mind as when you go to put things back together it’ll look like there’s not enough room to move the gearbox back into place. Don’t worry, as you edge things back together the hopup unit will move forwards out of the way, just don’t force things.
Inside the gearbox: With the gearbox out of the chassis, and if this is the first time you’ve seen a mechbox yourself it’s worth familiarising yourself with how everything works and where it should be, especially if you plan of taking the gearbox itself to bits. In these shots you can see how the tappet plate and fire select movements line up for safe/select
First signs inside the gearbox look good, there is grease visible in the right amounts and no metal shards (lack of grease and visible metal filings are symptomatic of poorly run workshops). My only slight worry is the angle of the gearbox nozzle which seems to be drooping alarmingly downwards.
Stripping the gearbox: This is the bit I normally dread. To be honest there’s no real reason to take the gearbox to bits.. but I have to if I’m going to show you guys what’s inside there. Ladies and gents welcome to the world of tiny parts and even smaller springs. :) …oh how I hate gearboxes.
You’ll need a decent philips and a decent flat blade screwdriver to take things to pieces. So no need to worry about picking up any torx pieces to take things apart, CA have built this with users that want to upgrade/service in mind.
Okay, first up, the fireselect levers do not need to be removed unless you want to remove the inner grip gearing itself (needs a 1.5mm Allen key). I’ve shown you how to do it here so that you can see the tiny little spring and rod that is contained in it. This spring/rod rubs against the frame as you rotate the fireselect lever and gives you the positive “click” between selections. I’d highly recommend making sure these are done up tight because as you can see the allen screw that secures the lever is only held on a simple flat surface you don’t need it to undo much to slide off. Loctite is the order of the day here. ;)
The first real stage to get the gearbox free is to remove the grip plate side screws, and the centre screw as shown.
With the grip plate removed, now have a look at the wrap around plate at the front of the gearbox. The two screws there need to be removed as that secures the gearbox to the front of the grip. With that removed, ensure the fireselect switch is set to safe and then slowly ease the gearbox out the grip pushing it by pushing on the motor housing itself.
On the RHS of the gearbox you’ll see a small spring on the surface pushing against the dark wrap around metal part you’ve just unbolted the gearbox from. This spring and the lever that it pushes against are loose and will fall out as the gearbox is removed, be careful otherwise you’ll be hunting for that spring on your carpet in a few minutes.
Right, that’s the gearbox free, now plate a flat blade screwdriver between the rear block on the top of the frame and the black plate. Carefully rotate the screwdriver and ease the plate off to the front. Be careful here as the top plate is made from pressed metal; there aren’t any sharp areas on this one, however there could be on your own. I’ve sliced my own finger ends open on an AK gearbox top plate (the TM AK box is much the same) and blood tends to be a bit of a pain to clean off the internals. ^_^
Before removing any screws, remove the plastic covers, there’s one around the rear of the trigger guard, and one plastic rod that goes through the entire box from one side (secures a cable).
Now you need to unscrew the two screws that secure the gearbox housing to the mechbox, the remove the outer screws around the edge of the gearbox frame. As you remove the last screw ensure the gearbox is on its side and held down securely.
Now press your index finger against the piston area, and plate a thin flat blade screwdriver between the two gearbox halves and separate them gently. With the pressure of your index finger you can hold the gearbox main spring down and keep the internals from flying out as the halves are removed.
While carefully still applying pressure ease the main spring out of the rear of the gearbox so that it’s no longer sprung, then remove the top half of the gearbox.
…you might want some wipes or tissues at this point, as things get pretty greasy from here on in.
Previous complaints of the non-TM AEG variety that related to the gearbox centred around poor greasing, and lack of adequate shimming. As you’ll see there’s plenty of grease on all gears, the piston and the moving parts. The silicon greasing used is decent tacky stuff so it stays on the gears and doesn’t fly off, although you can see a small amount of deposit towards the bottom where the motor attaches.
To save confusion I’ve noted the exact shimming arrangement found on this gearbox (note the sketch in blue). The gear dimensions and orientation are best compared to the half assembled gearbox image so you can see their official arrangement. Unusually there was a thin flat shim on the outside of the bevel gear’s RHS bearing.
As the shimming may vary through development I’d recommend taking note of how things are organised on your own gearbox as I have, so that you know how things go back together.
There’s a small anti-reversal latch next to the first gear that meshes with the motor (the beveled gear). You’ll need to ensure that this is in the correct position/orientation when you reassemble.
Again, it’s worth noting here that these are decent 7mm bearings, and not the nylon type found in TM gear that tends to break the second you take things to bits. Another interesting point of note is the fact that the spring and piston are not moulded together, so should you wish to vary the power of your CA36C (up or down) it’s dead easy to do so, and unlike the TM you won’t need to replace the piston itself.
Reassembly: Reassembly is funnily enough just the reverse of the above actions, but there are a couple of things you’ll need to do to get things right. Basically the gears and piston need to be in the right positions before you put the two gearbox chassis halves together.
The anti-reversal latch at the bottom meshes with the bevel gear. Replace the bevel and spur gear and spring the anti-reversal latch against the motor side of the bevel gear. Now turn these two gears backwards until the latch locks and the gears won’t turn any more.
With the spur and bevel gears locked in place, you can now put the last gear in, the sector gear. This should be put in place so that it is about to draw the piston backwards. Now put the spring and piston set back and ensure that the nozzle at the front of the piston is attached properly to the tappet plate (the black plate that goes around the piston and draws the nozzle backwards).
Personally I prefer mounting the gears all in one side of the gearbox, with shims and bearings in place, then fitting the other side of the chassis over that. You could also fit the bearings to the free gearbox chassis half, and try to align the gears with the bearings, but I wouldn’t recommend it.
As you mesh the two halves of the gearbox together, make sure the top protruding metal upright is in place, I’ve got everything back together and realised I’ve left it out myself before. If the bearings won’t fall into place careful poke them in the right direction with a screwdriver through the holes from the top or from the motor mounting hole.