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Old 04-28-2006, 07:07 AM   #1
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Default TB-02 Ball Diff Melting

I have TB-02R that I'm having problems with where the diffs want to melt together. I followed the instructions exactly to assemble them, but after about 2 races the car slows right down. I check the diffs & the plastic diff joints are fused to the metal parts. Has anyone had this issue. I'm on my 3rd set of diff joints. Does anyone know of any aluminum diff joints that can be picked up somewhere?
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Old 04-28-2006, 07:50 AM   #2
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The diff screw must be screwed in too tight.. too much pressure leads to heat, and it's certainly happnened to me before..

How much grease do you put on the diff balls? It should only be minimal, otherwise they can slip easier, and require you to overtighten the screw to keep them from slipping. Dip an allen driver tip into the grease, and just dab each ball once, that's it.

Sand the plates with 600 or 800 sandpaper.. this provides additional grip for the balls, meaning less tightening of the screw.. your diff will still move smoothly.

Do you just tighten the screw them until it stops, or do you tighten them JUST enough so they barely slip? Ease the screw in bit by bit, with each few turns test the diff until it's just enough to be HARD to slip with a decent amount of force, but not fully locked. After this, you should still be able to freely rotate the diff halves without much effort. Usually people make the rear diff a bit looser than the front diff.

Do you break it in? Get an old dogbone, cut in half and put it into a drill.. run it for 30 seconds, and test the diff for slipping again, adjust the screw, and repeat 2 or 3 more times. This will break the plates in, providing the groove the balls need to plant into the plate, and the screw will be adjusted for the change.

How's the trust bearing? Make sure it's not gritty and well greased with either Associated Black, or Tamiya AW grease, they've never failed keeping it running.

Make sure the threads of the diff screw and nut are clean, otherwise they can slip and either loosen the diff till it comes apart or tighten right up and start the melting all over.

How are the bearings inside the diff? If they're seized up, they'll just rub on the plastic, creating friction and heat, and eventual melting.. Make sure they're clean and free-running, with a drop of oil.

In the end, you'll have freely rotating diffs that don't slip. If you still hear slipping when you accelerate, just try tightening and testing them again as above, but never just tighten them till the screw stops. The thrust bearing and screw may be able to take it and still let the diff rotate, but the pressure heats up the balls and plate pretty quickly.
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Old 04-28-2006, 08:28 AM   #3
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Having owned a couple TB02s I'll tell you this the diff joints are junk.... Get the diff joints for the Tamiya EVO III(black) or the lightweight ones (white) these diff joints will build up a very smooth diff.... more than likely the D rings are slipping around on the diff joint causing all the problems. Get the EVO III diff joints and you should be set, I think along with the diff joints you will also need the little nut holders that hold the diff nut as the new diff joints do not have that built in... Good luck.
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Old 04-28-2006, 08:40 AM   #4
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I've had diff melt down issues due to my mechanic. Yes it was me on assembly. Check to make sure the screws for the rear diff cover are not swapped for the shorter rear sway bar mount. If you use the longer screws to mount the rear sway bar retainer, the screw will protrude into the housing and rub against the diff spur gear. This is easy to do and not easy to detect because there is not that much interference between the diff and the screw, but after a few laps the heat from the frictiion will melt the bevel spur and slow the car down. I also had the long thin diff screw break. go to evo III parts as mention on the above post. replace everything including the long thin screw that holds the assembly together.
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Old 04-28-2006, 09:19 AM   #5
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i have never had a problem with the diffs melting the only problem i had was that the diff was to loose when i first made the car then the first few minutes of running the diffs just fell apart so that was really my fault.
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Old 04-28-2006, 10:02 AM   #6
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The stock outdrives are simply junk. Use the Evo3 reinforced diff joint (#53627, the white delrin ones) instead. You'll need the nut "buckets" (to hold the 2mm nuts, since those don't have the molded slot for the nut like on the std TB-02 diff halves), and they are included in the "A" parts trees on TB-02s (it's part A5). And compress the diff spring a couple of times before you put it into the diff. Hope this helps.
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Old 04-28-2006, 04:15 PM   #7
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think the evo II and evo III has differential issues... due to the overtightening of the gear box..(some says they always stripped ther diff gears) look back for the thread of evo III and ask them.

hope this helps...
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Old 04-28-2006, 04:34 PM   #8
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Me thinks diff too loose and it is slipping causing heat build up
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Old 07-31-2009, 06:40 AM   #9
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Default The true problem in the diffs!!!!!

Quote:
Originally Posted by Jam-ehz View Post
The diff screw must be screwed in too tight.. too much pressure leads to heat, and it's certainly happnened to me before..

How much grease do you put on the diff balls? It should only be minimal, otherwise they can slip easier, and require you to overtighten the screw to keep them from slipping. Dip an allen driver tip into the grease, and just dab each ball once, that's it.

Sand the plates with 600 or 800 sandpaper.. this provides additional grip for the balls, meaning less tightening of the screw.. your diff will still move smoothly.

Do you just tighten the screw them until it stops, or do you tighten them JUST enough so they barely slip? Ease the screw in bit by bit, with each few turns test the diff until it's just enough to be HARD to slip with a decent amount of force, but not fully locked. After this, you should still be able to freely rotate the diff halves without much effort. Usually people make the rear diff a bit looser than the front diff.

Do you break it in? Get an old dogbone, cut in half and put it into a drill.. run it for 30 seconds, and test the diff for slipping again, adjust the screw, and repeat 2 or 3 more times. This will break the plates in, providing the groove the balls need to plant into the plate, and the screw will be adjusted for the change.

How's the trust bearing? Make sure it's not gritty and well greased with either Associated Black, or Tamiya AW grease, they've never failed keeping it running.

Make sure the threads of the diff screw and nut are clean, otherwise they can slip and either loosen the diff till it comes apart or tighten right up and start the melting all over.

How are the bearings inside the diff? If they're seized up, they'll just rub on the plastic, creating friction and heat, and eventual melting.. Make sure they're clean and free-running, with a drop of oil.

In the end, you'll have freely rotating diffs that don't slip. If you still hear slipping when you accelerate, just try tightening and testing them again as above, but never just tighten them till the screw stops. The thrust bearing and screw may be able to take it and still let the diff rotate, but the pressure heats up the balls and plate pretty quickly.



HEY HEY HEY!

I dont belive when you say over tighten or minimal grease the diffs?

Listen to me guys all out there having problems with TB02 diffs.
I got the same problem as you on my TB02. Is it really the diffs when loose or over tighten?

I dont thinks so!!

The problem is like, after a few fast runs you will hear a noise like grinding, and when u press the throttle its like not transmitting the power right?

thats all our problems right?

So listen to me so that you can fix your problems and stop bragging..
First of all, lets say the diffs are really weak that it melts fast.
So after the diffs have melted, I heard grinding, and I opened the gear box and remove the melted part of the diffs, and when I install it back, I heard the same noise like grinding when I press the max throttle..so I opened it again and thinking about whats that noise, I looked into the diffs and have concluded that, the problem now is not the diff anymore, when i put it back at the gear box and turn the bevel gear, thats when i discovered that the noise is coming from there, because when the diffs started to melt, the diffs loss like 1mm thick of plastic, thats why the diff bevel gears are not properly meshing with each other, so when ever you will press the throttle the diffs are moving sideways because of the 1mm thick plastic loss to the diffs because of melting.

So my advice is to grease it a lot of grease to avoid melting, and dont over tight it, follow the Tamiya engineers, they said tight it until it just wont slip, so do it that way. It is not necessary to put the balls into sandpaper, it will just make it faster to consume the diffs, believe me it wont slip if you put a lot of grease and not to tighten it, because the force applied to the diffs itself when the car is placed on the ground is enough force.

Thats right you read it right, the dog bones are the links to the diffs and the wheels right? So when you put it on ground, the weight of the car is distributed to the four wheels, so example 2lbs.

P=F/A so 2lbs/1inSq
2lbs/in sq. / 4 = 0.5lb/in sq.

that is what you diffs each side is getting 0.5lbs/in sq.

isnt that enough to press the balls of the diffs? I think so!!!


My advice to you all is that when you got problems with your TB02 and you thougth its your diff to loose or to tight, or slipping, fine! But when you saw that it looks ok, then maybe you already got a high tolerance from the melting thats why your bevel gear dont mesh properly.

If you have questions feel free to ask me.
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