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Hi folks.

I recently picked up a couple of WT01s.  With the first, within 20 minutes of running I started getting a grinding from the gearing on acceleration, especially from a stand still.  I've pulled the gearbox apart and had a really close look at everything, I couldn't see any obvious sign of any grinding gears, but I replaced the diff gears and the final drive axles.  It was a lot better for about 5 minutes then it was back to grinding and loss of drive again.

The other kit is waiting for paint so I swapped over the gear and motor block, sod me if I haven't just seen exactly the same.  Perfect for the first few minutes, then grind and loss of power.  I haven't taken this gearbox apart yet, but it's exactly the same sound, so I doubt - without advice - I'll see anything untoward.

I'd heard these gearboxes are nearly indestructible which is why I bought them as first use bashers, but at the moment they're both in the garage.

Has anyone found this?  Or know where I should start to look?

Thanks.

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There are two 9mm washers in the differential.  

If those were left out by mistake, it would create too much gap.  The differential could slip, then. 

5a3c144e0a9f3_WT01Diff.jpg.2e5f34fac321cd06fa2bbc84484ae152.jpg

You could adjust the pinion mesh for either 18t or 20t pinion.  Aside from that, all the gears have big axle shafts that allow no adjusting. So there is no way you could mismatch it.  As you have heard, it's a bomb-proof gearbox that has been in production for over 15 years.  I have Wild Dagger that uses 2 identical gear boxes front and back for 4x4,  And I have Wild Willy 2, which uses the same gearbox.  I never had any problem.  I hope this helps.   

 

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Could it be loose pinions perhaps? Fine when cold but after the motor and shaft warms up a bit the pinions start to slip. Either not tightened enough, no threadlock or the grub screws weren't screwed against the flat on the motor shaft.

The only other thing I can think of that gives a similar effect is a hex drive rounded off so the pin is slipping or perhaps the pin is bent and comes out of place. When that happens though the pin usually disappears.

Loose tyres? 

Just random guesses, not trying to suggest you can't tell between the sound of a loose tyre and slipping gear lol.

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As others have said, this is a very very tough gearbox. And you have checked it. And it has affected not just one but two gearboxes. I thus suspect that whatever it is merely sounds like a gear issue.

Now what could sound like a gear issue but not be a gear issue?

Perhaps the motor bearings or bushings could be shot? Perhaps it is an electronic fault causing high frequency juddering? Umm... Any other ideas?

 

@MuntyScruntfundle: I don't suppose you could upload a video of the issue?

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Hello all, with the WT01 gearbox i had two issues you may look at. First is part MA12 in the diff with the tree arms where the small bevel gears are running on. They break off the centerpart if to much torque is applied, therefore the bevels come lose and can not mesh with the bigger bevels anymore and the diff starts slipping and creating noise. Second thing to look at is the bigger bevels MA10 splined hole, the splines get damaged if excessiv torque is applied, e.g. landing a jump with full throttle, then the splined shafts of the drive cups wheel free in the hole and the grinding noise starts.

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The washers are there, I made sure they were replaced for new.

The motor shafts are tight, these definitely aren't a problem.

The hex nuts, well, I printed some new ones that are perfectly snug and cannot slip.

I can't think that 2 motors can come out defective from two different suppliers, they feel fine on basic inspection, and I'm not losing motor rpm, I'm missing the power further along the drive train.  The 'clicling' isn't fast enough to be the motor, it's somewhere near the wheels.

 

I've just had a quick look at box 1 again all locked down on the bench, full throttle, no slip.  So, there's no problem when everything is cold and dry.  On both occasions I've tested on damp grass, but I can't think water is going to get anywhere that's going to cause a problem.

I think tomorrow, I will send one of them out for a damp run and dismantle as soon as I get back in.  My suspicion is the diff, the sound is more metallic than plastic and there are definitely no bits of plastic floating around.

It's so strange no one else seems to be complaining of the same thing, but I have two with the problem.

I will report back tomorrow.

Thanks folks.

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The above is from a.w.k. is true - if you are putting a shedload of torque through the system. However most 1/10 scale power sources wouldn't do this to a WT 'box. What motor/ESC/battery are you running?

 

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35 minutes ago, a.w.k. said:

Hello all, with the WT01 gearbox i had two issues you may look at. First is part MA12 in the diff with the tree arms where the small bevel gears are running on. They break off the centerpart if to much torque is applied, therefore the bevels come lose and can not mesh with the bigger bevels anymore and the diff starts slipping and creating noise. Second thing to look at is the bigger bevels MA10 splined hole, the splines get damaged if excessiv torque is applied, e.g. landing a jump with full throttle, then the splined shafts of the drive cups wheel free in the hole and the grinding noise starts.

I actually had an HBX bonzer with the arm snapped off the MA12 part now that I think of it.

 

18 minutes ago, TurnipJF said:

The above is from a.w.k. is true - if you are putting a shedload of torque through the system. However most 1/10 scale power sources wouldn't do this to a WT 'box. What motor/ESC/battery are you running?

 

Don't forget some people have no concept of coming off the throttle after jumps etc though. If the previous owner was like that it could be feasible. That puts a huge strain on things even with modest power.

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Quick midnight update, I've just ragged the badword out of it on the drive way which isn't at all as wet as the grass, no problem.  Not a single click or grunt.

So, it's a problem with something getting wet.  I'm still confused!

Also it hasn't had any hard hitting or landing moments, grass or smooth tarmac.  I think somehow the diff is slipping when it gets wet.  But I can't see how water would get to the diff, I know it's not a sealed box, but still.

Edited by MuntyScruntfundle
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What motor and ESC are you running? Sensitivity to water suggests an electronic source of the trouble.

 

Unless of course your tyres are slipping on the rims when wet. If one tyre slips more than the other, the diff would be running, possibly quite fast, and making a metallic noise as it does so. 

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With the splined shafts of the drive cups and the larger bevel gear MA10 i had another issue in the past, when they have enough play to come out of the diff, the loaded area is proportionally less to transfer the power to the wheel, so they are prone to get damaged a lot easier as when they are fully seated in the diff. As one side of the diff is enough to get trouble with power transfer take a look at both sides if the splines in the bevel gear MA10 are intact or not.

Did also you move also the motor to the other car ? I had motors screaming because of a motor bearing running dry.

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I can't help with the solution, but I've had this with my 4x4x4 build of this truck with double brushless. Everything has been tight when I've checked it and I've not been able to work out how to make it happen reliably...watching this thread with interest 

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I did a bit more testing today in the wet grass.

As someone suggested above, it's the bloomin tires slipping on the rims!  or at least one tyre slipping.  It's been difficult to work out, because it happens at full throttle and the things are so fast, add my wheelchair so I can't move around that easily, add wet conditions only, add loads of other stuff!

I decided to put the iPhone to work and filmed the car from both sides to see if I could see the suspension dipping as the weight moved backwards, then I'd know if there was any power getting to the axles, and in the slowmo you can see a rim spin up while the tire stands still.  Of course to further complicate matters this will only happen on one side as there's no limited slip in this diff setup.

So, there you go, Zomboided, get the phone out and slowmo both sides from standstill to full throttle, I wouldn't at all be surprised if that was the problem.

Partly WooHoo for finally getting to the bottom of the problem, and a slight sigh as I have no idea how to stop a tyre slipping without gluing them, which I really don't want to do.  Maybe something like UHU which wont melt into the plastic?

And while on the subject of tyres, does anyone know where I might find rims and tyres this size?  I know they're classed as 10:1 Monster Truck, but on the sites I know and use there are only these wheels and tyres.  I could really do with some softer rubber and some inserts.  Oh, and tyres that don't slip!!

As always, any suggestions will be very gratefully received and I thank you all for your input, it really did help.  :o)

Cheers.

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There was a thread on here recently (well, November) about tyre glueing.

The distilled answers came out as pound shop superglue or silicon sealant.

Hope that helps!

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No need for glue. Just place a rubber band in each bead of each wheel and install the tire over it. The rubber band takes up the gap and adds enough friction that the tire doesn't slip.

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https://imgur.com/a/QFmE2

I asked the same question about alternative rims some time back. I landed on HPI Classic King wheels for the shelf and Blackfoot 3 wheels for running. I also have a set of HPI Superstar MT wheels for a Monster Beetle project.

The Classic King wheels need to be about 3mm more offset - if these were runners I'd look for an extension solution. The Superstars seem to fit nice but I've not run them on the truck (work fine on the Beetle). From memory these wheels come in different offsets...the Tamiya wheels are very deep, and you need to get the closest to that to make these work.

For tyres, I've stuck with the Blackfoot 3/Monster Beetle tyres, and a set of Blackfoot tyres for the shelf. I'm happy with the Blackfoot 3 tyres for bashing, but if you find something better, post it up!

Thanks for the hint about moving my problem forward...that's some clever thinking. I reckon it's worth doing the rubber band thing anyway.

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