AEG making high-pitched "Squeal" sound when fired? (updated)

[Mr. G36!]

You know how a new, healthy AEG makes a low-pitched "Pfft" sound when you fire it? Well mine's making a high-pitched "Squeal." It shoots okay, but the range is kinda craptastic, and the hop-up seems kinda off, but that shouldn't affect the sound. Gearbox? Motor needs adjustment? Maybe I should just run a bigger battery? I dunno, I've never seen this before...

...anyone got a suggestion?

-Update-

I pulled the motor out completely and the last half portion of all the teeth look ground down by a good milimeter. It still runs though; they haven't been stripped flat. I'm thinking the JG brand just doesn't like the Guarder body, but I'll try a different pistol grip just to see if that makes any amount of difference.

If not, I might try a Guarder mechbox and motor instead, since I'll have to replace the motor anyway, and given the condition of that, probably the gears in the mechbox that mate with it at the very least as well.

[Azathoth]

Most likely poor shimming or motor height issues

Look at your pistol grip. You will find a grub screw or a standard screw where you can adjust the height of the motor. Adjust it until the gun makes the least amount of noise. If the noise persists. Either the adjustment screw isnt doing the job because the motor is jammed in the pistol grip OR it's shimming. Take out the motor and make sure it can freely move up and down inside the pistol grip and is not being bound by the wiring; and if required you have the motor plate in your grip

[ThunderCactus]

Are the motor wires both run down the stock side of the grip? Because if ones in front and ones in the back it would cause motor misalignment and therefore squealing

[CJay]

Ok let's eliminate the obvious first an that means we need details. What brand gun etc. Stats? Some guns just come with a bad motor. My first suggestion is try with a high torque motor before cracking the box. No point going and getting an impact hammer when the toffee hammer is all u need

[Mr. G36!]

Ha ha, yeah, I'll elaborate a bit.

The mechbox and most of the other internals are Jing Gong. I pulled the guts out and gave it all a nice metal body; never opened the mechbox itself, and it never squealed before, so I don't see how it could be a problem with the shims.

I did give the motor a bit of an adjustment, and it seemed to help a little bit, but the squeal isn't gone entirely. And no, the motor wires are both at the rear of the pistol grip in the appropriate groves, so they shouldn't be interfering with the motor.

I gave it a few shots, and it sounds like the squeal is coming from around the magwell, but that's probably just because it's the only substantial opening in the body. It's certainly not coming from the pistol grip, where the motor is. I'm assuming it's either the gears or the spring, but like I said, it didn't make this noise before I swapped the bodies, and I never opened it, so I don't know what would be different now as opposed to then. It seems to shoot okay, aside from the hop-up not quite fitting properly and not really doing much (gonna replace it at some point).

Maybe the battery, which is kinda old and is only an 8.4V mini, just isn't packing enough punch, and as such the motor just can't put out enough power to turn the gears fast enough? I'll charge up a 9.6V and give that a try, just to see. Other than that, any ideas?

[ThunderCactus]

It shouldn't squeal at any speed
Did you run both motor wires down the back of the pistol grip?

[Mr. G36!]

Yup, along these recessed grooves that keep them from pushing the motor forward.

[twistidpair]

This might sound like a lot to do but I would change back to the original body to see if it runs fine... It really does "sound" to me like it is the motor/bevel gear is not mating properly.

[Azathoth]

you have have over torqued screws etc that hold the gearbox in place such as the buffer tube screw, pistol grip screw. Also retaining pins could be off centre.

Probably poor qc on the spec of the body

[ThunderCactus]

good point, try loosening the buffer tube screw and see how it sounds

[yuhaoyang]

metal body of poor quality could hold the mechbox a weird way.
did you make sure the pistol grip screws are in a diagonal pattern as before? Could try getting a new pistol grip from the same manufacturer if nothing else works. Do JG motors have a motor plate or bearing? Maybe that is missing?

[Azathoth]

I just did some experimenting with a gun in my hands from JG. I opened up the gearbox and re-shimmed and greased and dropped it into my Magpul body and their are no problems. When i drop it into my G&P body, no problem. The King arms body I have laying around I had problems getting the gearbox into position and after i put in the centre pin the gearbox and the body didn't line up for me to be able to put in the rear retaining pin.

The JG gearbox has some similar problems with the JG body as well, however the owner already filed down the rear receiver hole to give clearance for the pin.

[Mr. G36!]

Nice little update here, for ya'll.

I pulled the motor out completely and the last half portion of all the teeth look ground down by a good milimeter. It still runs though; they haven't been stripped flat. I'm thinking the JG brand just doesn't like the Guarder body, but I'll try a different pistol grip just to see if that makes any amount of difference.

If not, I might try a Guarder mechbox and motor instead, since I'll have to replace the motor anyway, and given the condition of that, probably the gears in the mechbox that mate with it at the very least as well.

[ThunderCactus]

That's a consequence of having your motor height set incorrectly

[Mr. G36!]

I guess so. Though any higher or lower and it wouldn't work at all. Lower would have the gears either clip or just spin without contact, and much higher would just sorta sieze it up and nothing would happen.

I kinda think that the alignment is off, though I'm not sure if that's because of the pistol grip or the receiver.