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Super ally

Novafox diff problem.

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I have just finished building my novafox and had heard that the gearbox was weak in this buggy.The diff seemed to be what was the problem with the novafox,so i took care when building the gearbox and making sure i made no mistakes.I took it out for its first run and sure enough after 5 min the gearbox started making a cracking noise so i stopped.The diff had gone as i had feared,i will have to strip the gearbox and probably have to buy new gears.Do any of you have any ideas what i can do to stop this happening again as iove this buggy and dont want to have to shelve it.Thanks.

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Just want to add a bit more info about this issue,when i holdĀ the buggy off the ground and throttle forward and reverse there is no clicking sound.The clicking only happens when going from reverse to full throttle.

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My original Fox back in the day never had any trouble with its gearbox (other than wearing out a couple of motor pinions) despite huge amounts of use. I don't know if the rere is somehow weaker, but I wasn't aware of it being a weak point.

When you saying going from reverse to full throttle, what do you mean? Do you mean going flat out backwards and then slamming it into full throttle forwards? If so, whilst turning (ie to do a J turn), or in a straight line? I imagine full speed backwards to full throttle forwards would put a LOT of strain on the gearbox on a RWD buggy on a grippy surface, if that is what you mean.

Other than that, the only issues I can think of would be if you've got the pinion spacing wrong with that funny shaped washer thing, and the clicking is actually the pinion skipping teeth, or if the diff gears are on the wrong sides (I seem to remember the left and right ones are not identical), but you said you were sure there were no mistakes, so probably not either of those.

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28 minutes ago, Super ally said:

The clicking only happens when going from reverse to full throttle.

The doctor would say "then don't do that" B)

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Check your motor screws. Ā I had clicking in mine going to reverse and it ended up being one of theĀ motor screws came loose allowing the motor to move around. Ā I didnā€™t notice until I put a screwdriver on it.

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40 minutes ago, AJB123 said:

My original Fox back in the day never had any trouble with its gearbox (other than wearing out a couple of motor pinions) despite huge amounts of use. I don't know if the rere is somehow weaker, but I wasn't aware of it being a weak point.

When you saying going from reverse to full throttle, what do you mean? Do you mean going flat out backwards and then slamming it into full throttle forwards? If so, whilst turning (ie to do a J turn), or in a straight line? I imagine full speed backwards to full throttle forwards would put a LOT of strain on the gearbox on a RWD buggy on a grippy surface, if that is what you mean.

Other than that, the only issues I can think of would be if you've got the pinion spacing wrong with that funny shaped washer thing, and the clicking is actually the pinion skipping teeth, or if the diff gears are on the wrong sides (I seem to remember the left and right ones are not identical), but you said you were sure there were no mistakes, so probably not either of those.

Yes i mean when in reverse then going straight into forward it makes the clicking noise.

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2 minutes ago, tamiya3speed said:

Check your motor screws. Ā I had clicking in mine going to reverse and it ended up being one of theĀ motor screws came loose allowing the motor to move around. Ā I didnā€™t notice until I put a screwdriver on it.

I will check that,thanks.

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I keep blowing up gearboxes on my Fox. 15T brushed motor.

Actually, it doesn't seem to matter which motor I use. I eat gearboxes like they were popcorn. Built a Novafox transmission for it. Doesn't do any better.

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5 hours ago, Mrowka said:

I keep blowing up gearboxes on my Fox. 15T brushed motor.

Actually, it doesn't seem to matter which motor I use. I eat gearboxes like they were popcorn. Built a Novafox transmission for it. Doesn't do any better.

It seems to be a weak point on these buggies,it's a pity as i think they look great.

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I gave my Novafox an absolute thrashing a couple of weeks ago, with a 10.5 brushless motor and a 17t pinion and didn't have any gearbox issues at all. I'd not heard about any

issues before either. Very strange!

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I think the going from reverse to flat out full throttle would be enough to make even the hardest of hardened gearboxes and diffs wince! Particularly with the torque available with modern motors.

Isnt this a mechanical sympathy issue as opposed to a defect?

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I probably bang on the transaxle on my Fox and good luck getting my seven year old not to do that....

Still, my Kyosho re re diffs tolerate all kinds of abuse from us and worse, since the re res all are driven by powerful brushless motors.

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Yeah I have a high 3000 kv brushless in my novafox (something like a 3700) which I've had from new when originally re released and never had a bother with clicking and it does shift, with it such a light weight chassis. Sure you've got gear mesh etc correct? Does itĀ onlyĀ do it when going full reverse to full forwards? If so, I agree that it might be a little too much for these very old designs.

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As I said, I never had any trouble with my vintage Fox's gearbox. It still works perfectly today. It wore out a couple of motor pinions, 2 sets of driveshafts, the original motor (brushes disintegrated), but never a single click from the gearbox or diff (other than the horrible noise once the motor pinion has no teeth left any more - but the spur gear even survived that and it's still got the original one it it).
I don't know if there are any difference between the rere and vintage gearboxes (other than the much stronger driveshafts in the rere).

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Never had a problem with my novafox. Check your motor pinion and the alum spacersĀ 

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3 hours ago, Silver-Can said:

Yeah I have a high 3000 kv brushless in my novafox (something like a 3700) which I've had from new when originally re released and never had a bother with clicking and it does shift, with it such a light weight chassis. Sure you've got gear mesh etc correct? Does itĀ onlyĀ do it when going full reverse to full forwards? If so, I agree that it might be a little too much for these very old designs.

Gear mesh is right and diff is smooth when i rotate wheels by hand,no noise from gearbox.When i hold the buggy off the ground and use forward and reverse there is no clicking at all but when i put it on the ground and hit forward then it clicks.Don't understand what the problem is.

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11 minutes ago, rwordenjr said:

Never had a problem with my novafox. Check your motor pinion and the alum spacersĀ 

Motor pinion is ok.

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9 minutes ago, Super ally said:

Motor pinion is ok.

Check the plates according to what pinion size youā€™re using. If itā€™s correct, take apart gearbox and take pics of it

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5 hours ago, Silver-Can said:

Yeah I have a high 3000 kv brushless in my novafox (something like a 3700) which I've had from new when originally re released and never had a bother with clicking and it does shift, with it such a light weight chassis. Sure you've got gear mesh etc correct? Does itĀ onlyĀ do it when going full reverse to full forwards? If so, I agree that it might be a little too much for these very old designs.

Now it does it on hard acceleration sometimes.

Gear mesh appears fine.

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You are going to have to replace the gears, and understand there is no slipper clutch. Going from "reverse to full throttle" only once will destroy the gears.

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1 hour ago, Hobbimaster said:

You are going to have to replace the gears, and understand there is no slipper clutch. Going from "reverse to full throttle" only once will destroy the gears.

I have looked on ebay for new gears but none for sale at moment.

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This happens on mine too.

the problem is the small cog on theĀ counter gear that the pinion drives the large side of, slipping against the diff gear. Iā€™ve had about 8 runs on a 15t motor and need a new counter gear as the teeth are semi stripped,Ā none seem to be about!

was wondering if the Blitzer beetle one is the same size?

I think itā€™s loose manufacturing tolerances in the gearbox mount for that gear, just allowing it to move slightly so the teeth slip, that or a sub standard batch of gears themselves.

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19 hours ago, Super ally said:

Gear mesh is right and diff is smooth when i rotate wheels by hand,no noise from gearbox.When i hold the buggy off the ground and use forward and reverse there is no clicking at all but when i put it on the ground and hit forward then it clicks.Don't understand what the problem is.

That might be a drive shaft issue. Try holding the car off the ground whilst simultaneously pushing the rear suspension arms up (to imitate the angle the arms/driveshafts etc would be if on the ground ie near horizontal) and see if it makes the sound then.

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5 hours ago, Silver-Can said:

That might be a drive shaft issue. Try holding the car off the ground whilst simultaneously pushing the rear suspension arms up (to imitate the angle the arms/driveshafts etc would be if on the ground ie near horizontal) and see if it makes the sound then.

Tried what you have said and there is no noise from gearbox but when i put it on the ground and hit forward then it clicks.

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