View Full Version : Reinforced gearbox recommendations?

05-09-2003, 08:07 PM
A couple of weeks ago my M4 failed at Hunters. At the time, I thought it was a stripped gear or piston, judging from the free-spinning noise coming from the gearbox.

Today I actually took a look inside the M4 and found that the forward section of the gearbox, around the nozzle, had cracked badly. As a result, the spring was able to push the nozzle/piston/cylinder assembly further forward than is normal, such that the sector gear could no longer catch the piston teeth.

So, I am soliciting opinions on replacement gearboxes. I'm looking to get a reinforced shell so I can transplant the internals from the cracked box, not one of those pre-upgraded boxes. Based on some quick searching I've done, my default choice is the Systema Fastec/Progear shell.

I'm wondering if anybody has any opinions or recommendations that would suggest a potentially better option. I'm hesitant to go with the Classic Army box, just because of the "you get what you pay for" rule. I've also looked at some of the custom gearbox shells which use 7mm bearings instead of bushings, but I've heard it said that bearings are not quite as reliable as standard metal bushings.

Any advice or wisdom would be appreciated. Thanks.

05-09-2003, 09:28 PM
Not being unfortunate enough yet to actually have a mechbox break on me, all I can do is go off of info already out there.

The CA ones are supposedly tough as hell, but being CA I bet there are subtle QC issues from mechbox to mechbox. Some will probably be excellent, while others might just give you hell.

The thing about Systema parts is that they always seem to fit well and not have the QC issues.

In all actuality, I would probably either just get another stock mechbox (since I haven't had one break yet) or spring for a Systema/Progear. I'm just wondering if it would behoove the buyer to just go with the stock TM mechbox shell since you can buy two of them for the price of a Progear mechbox, which doesn't seem to be any more of a proven commodity.

Some threads:


I'm hoping someone with direct experience can offer more thoughts.

05-09-2003, 10:07 PM
So after reading a few positive things about the Classic Army box in the links that Wolv posted (Thanks!), I looked around a bit and it seems like the guys at The Q Project are well impressed with them:
Naturally, it's a product they're trying to sell, but their claim that it will handle their Level V upgrades (480+ fps) is not to be scoffed at.

Reliability is my main goal, so the CA has my attention for now. I guess I'll wait to see what's up with the Airsoft Ohio forums to do some more searching.

05-10-2003, 12:08 AM
Classic Army makes great mechboxes. They are almost identical to the progear mechboxes. The biggest issue is that you can and probably will have issues fitting them into the gun. If you have a metal body you can guarantee issues. I put a systema progear mechbox in a systema Metal body and it would not fit. It took Jason and I a bit of bending and hammering to get it to fit. If your interested I have a stock mechbox shell that I snagged off arms deals that I would part with for 25 bucks.

btw....congrats on accomplishing the impossible hehe.

05-10-2003, 01:49 AM
For $25, that stock box sounds pretty enticing, durability be damned. I'll drop you a PM about it, thanks.

05-10-2003, 02:59 PM
The vast sum of my personal experience is with an Ichi mechbox. The M4 Tac that I've been running upgraded internals in for the past 3 years came with an Ichi and it still looks as solid as the day it was purchased. Somewhere I had read that Ichi wasn't that good, but I suppose like most things, sometimes you get a lemon and sometimes you get lucky.

As of this moment, I'm still running it and two newish Progear mechboxes I picked up a couple of months ago.

05-11-2003, 06:43 PM
I've had (and seen) several gearbox failures of the type your describing and I'd be willing to bet the cause is repeated dry-firing. Without a BB in the barrel, the piston slams much harder than normally when its released by the Sector Gear. Stock gearboxes aren't strong enough to take those kinds of forces and will crack eventually.

Another area you may want to check is your hopup. Look to see if its cracked around the back of it, on the side where the adjustment dial (large gear) is on the hopup body. In most of the gearbox failures where the front of the gearbox has seperated, the hopup was broken too.

Regarding gearbox shells, I'd suggest staying away from CA reinforced gearboxs for one reason: quality is hit and miss. You can get one gearbox that works great, then get another that is nothing but trouble. The most common issue I've seen on CA gearboxes is an intermittent problem with the Antireversal Latch.

One some CA gearboxes, after you've installed all of the parts and reassembled the gearbox, the latch does not function. In other words, it fails to prevent the Bevel Gear from spinning backwards. If that happens, you'll have serious problems with performance and possible damage to your gears and/or piston, especially if your using a High-Torque or Infinite Gearset.

I've had some of my most frustrating moments dealing with this specific issue. And I've been unable to find the cause of it in most of the instances where its happened. The only way I've been able to resolve it was to modify the latch and the Bevel Gear and I did that as a last resort. The other time, the issue was caused by what I believed to be a mistake in casting the gearbox shell. The latch geometry appeared to be off when compared to a Marui OEM gearbox. The other times, I could find no discernable cause of the problem, other than the fact that the gearbox was made by CA.

Thats been the most frustrating, when you know you've checked everything and done all you can, and the problem still exists. Its for that reason, and the hit and miss nature of CA gearboxes, that I use Marui or Systema Progear Gearbox shells exclusively.