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Old 03-23-2012, 07:45 PM   #1
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Default Gear Diff

Will the TB03 Gear Diff assy will share are interchange with Tamiya TB EVO3 or EVO4 ?
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Old 03-24-2012, 02:27 AM   #2
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Have you measured the width between the bulkheads?
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Old 03-25-2012, 03:15 PM   #3
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Default A few measurements to get started.

I've wondered the same things so I measured up a spare TB02 housing and gears as they are shared with the EVO3.

1 The height from the bottom of the gearbox to the centre of the bearings/diff outdrives is 19mm.
2 The width available inside the diff housing is 23.3mm.
3 The width between the ridges which hold the bearings in is 31.5mm.
4 The bevel pinion gear has 15 teeth and an outer diameter of 14.9mm.
5 The diff ring gear has 39 teeth and an outer diameter of 32mm.
6 The final drive ratio is 2.60 (39/15).

I just looked at the manual for the TB03 and the TB03 has a 16 tooth bevel pinion gear in its diff housing giving a final drive ratio of 2.438 (39/16). The bearings which support the diff are the same size in both cars (10mm ID, 15mm OD) so at least 2 factors come into play.
1 Will a TB03 diff with bearings fit in the 31.5mm width available?
2 Will the diff mesh properly with the 15 tooth bevel gear, with or without shimming?

I don't have the TB03 diff parts or housings to measure them, but if someone else does we may be able to figure it out.

Hope this helps, Justin.
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Old 06-21-2012, 01:03 AM   #4
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I have an EVO 4 and will take some measurements. I would like a gear diff in the Evo 4, the spool is VERY rough on the front diff pinion gear, I have been through a few.
I am running a Yeah/3Racing (cant remember which) ball diff assembly at the rear so I think the diff width is compatible with EVO3 & TB02, but I dont think the TB03 units will fit in. I also recall that the EVO 4 has a different internal ratio, so gear diff toothcount will not be compatible.....I may have to run front and rear ball diffs, and just crank it up really tight at the front with ceramic balls so that they dont 'flat'
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Old 06-25-2012, 03:40 AM   #5
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I checked on my TB03 and the Evo 4. The diff width is fine, the tb03 gear will NOT mesh with the bevel gear. I also tried using the bevel from the tb03 and there are still some clearance issues, so not likely to work. The other consideration is that the plastic dust covers on the diffs foul the gear diff do if you could get it to work, you would need to run without the covers.
Not sure what your motivation is to run the gear diff, but mine is because the spool is hard on the drive train, especially if you bump a board under throttle, it crunches the diff gears. The one way is useless on my track and a ball diff done up too tight is not a great alternative. I might try some harder diff balls, but I suspect they will mean diff rings will get scored quickly. A shame there is no gear diff that will fit the Evo 4, but I reckon the Evo 5 shares parts better with a tb03, dunno if the IDR is the same though.
A few years back I created a 'tough' diff by using friction pads instead of balls, it was almost a spool, but had some 'give' in te event of crash or locking, might try that as an experiment.
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