Noisy Lunchbox Gearbox...

[Grumpy pants]

I stripped clean and reassembled our L.B gearbox and it's still noisy when we run it.

I've put new bearing in and fresh ceramic grease..it doesn't effect the truck, it's just a bit frustrating.

It used to have a brushless set up in it and now it's a standard 540 motor.

My guess is worn diff.

Any suggestions would be appreciated.

[pizzachaude]

Hmm, had this problem in a Hornet gearbox once. Turns out the outer diff gear was cracked and was spreading apart under load. Looks like you've checked all the obvious stuff (bearings, grease). What pinion are you using? If its the stock aluminum one it could be worn out (will have sharp teeth). Just a thought...

[Burmanater]

Well from what I've seen with my 18turn brushed motor. You could have very well worn the plastic teeth on both the gear that contacts the motor gear and the larger ring/spider gear in the center. I recently stripped mine. I couldn't imagine what a brushless would do. What's this aluminum gear you speak of pizzachaude? Might be a worthy upgrade over the factory plastic in the LB/MP.

[XV Pilot]

The LB uses a hard brass pinion, which unlike the aluminium one used in the Hornet, tends to last very well. Unless your LB has been seeing a great deal of use, the pinion should be okay. Wouldn't hurt to check I suppose, since you say you were running it on brushless.

Could the issue be with the motor itself perhaps? Is it seated squarely on the motor mount, are the screws all tight and the bearings/bushings in good nick? These things could potentially affect gear mesh.

[GregM]

I managed to crack my Hornet's gearbox once due to having screwed together the plastic halves too hard. Other than that, all the gears were still fine.

It's best to check on the Lunchbox:

1. Condition of all gears, ball bearings and plastic parts of the gearbox. The LB long 10T pinion is made of brass and should last longer than aluminium ones, but I assume it isn't as tough as steel ones.

2. When assembling, be sure the small bearing and supplemental small parts like the small metal pin spacer are there.

3. Motor mount assembly: Often the plastic Lunchbox motor mounts are cracked due to having experienced too much force on assembly. Be kind to the mount and use a small amount of Tamiya threadlock for the long metal screws that go into the metal hex nuts of the mount. This way you can drive the screws in gently until they are firm, but they won't get loose by themselves from vibration. The problem with cracked mounts is even more present on the Blackfoot/Monster Beetle/Mud Blaster.

4. Be kind to all screws that drive into plastic. The plastic will thank you for that and ensures that you can disassemble and reassemble your car repeatedly without having to worry about stripped threads. Correct screw drivers (Tamiya JIS screwdrivers instead of regular Philips ones) key better into the Tamiya screw heads and make it easier to get driving the screws in right.

[pizzachaude]

Sorry for the confusion, I thought the pinion was aluminum like the hornet

[GregM]

Sorry for the confusion, I thought the pinion was aluminum like the hornet

No harm done. Cheers

[SteveU30]

Is it noisy when cornering or in a straight line? If only when cornering then it's more likely to be the diff internals. One way to find out for sure would be to lock the diff temporarily and see if the noise goes, if not then the diff internals are fine and it'll be one of the larger gears (pinion, counter or differential spur).

[Grumpy pants]

Thank you chaps for all the info and tips, I appreciate you taking the time to respond.

The gearbox casing is all fine, no cracks or damage.

The pinion is the standard brass 10T L..B one.

I use the lovely Tamiya screw driver set, the blue one!

The internals didn't look damaged or worn, but it was noisy when we bought the L.B second hand with the brushless set up in it.

We are now running the standard silver can and its noisy when driving straight ahead, I'm not sure about when turning though.

I'm going to take it a part and examine everything very closely and replace the main initial cog that is turned by the pinion and go from there.

[GregM]

I've got the blue toolset, too. A great quality set, isn't it? I wish you good luck on finding the source of noise in the gearbox. Please let us know if you've found it.

[Grumpy pants]

Thank you everyone for the tips and info.

I intially changed the diff and gears with no luck and tonight I changed the pinion and the large initial cog.

It's all good now, my guess is that general wear and tear from the previous brushless set up had taken its toll.

It cost a massive £8.45 inc post and packing.

I get the feeling it's as quiet as I can expect an L.B gearbox to be now.