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TD4 diff slop

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Well, I've been slowly enjoying my fresh new TD4 build until things came to a thudding halt like skateboarding into a ball pit. I knew from reading older posts that the diff needed more shims than what was provided to stop the diff's side-to-side play. What worries me is the rocking motion denoting excess clearance between the diff's support bearing's outer race and the molding. That's the kind of slop that effects mesh. Any ideas? The best I can come up with is foil or thin shim stock wrapped around the outer bearing race in an attempt to take up the excess clearance from what I presume to be poor molding tolerances.      Shoulda started my Egress first, lol.

 

 

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That does seem excessive. I had a Redcat years ago that I had to wrap the outer part of the bearings in teflon tape to get a good snug fit. Something I wouldn’t expect from Tamiya.

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I had sideway movements on DN-01 Zahhak. It didn't affect mesh, but I feared it could make a dogbone fall off. Shims were fine for that. 

If foil is too thick, you could try degreasing on the outside of the bearings and use a long piece of Scotch tape? I wonder if even that is too thick. I often discover how little the gap is, even when it's wobbly like that.  

 

 

 

 

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This is really a pet peeve of mine with some Tamiya builds. Nothing worse than installing a nice precision ground ball bearing and it just falls loosely into the recess. Something that just came to mind would be to mix a tiny amount of epoxy and put a thin coating on the outer race and around the receiving hole then press the bearing in. It would be semi permanent but could be removed if necessary. A little would go a long way. As Juggular mentioned the gap is deceivingly small.

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Looking things over I found this on the gear cover:

20240217_160739

 

See those three little rectangular protrusions? Well, they do stand proud of the mating surface (the middle one is particularly noticeable in this pic). Perhaps trimming them and carefully flat sanding the cover mating surface on a piece of glass slightly will help. I measured about .001" to .002" variance from the depth of the recessed screw mounting holes (two visible in this shot) and the matching nubs that lock into them on the chassis side (the nubs being shorter), so I have a little bit of wiggle room to tighten things up. If that doesn't suit satisfactorily, I'm going to try @Juggular 's tape idea to start. 

I knew this build wouldn't be perfect from combing over post and reviews but it was a little jarring to be humming along, fascinated by the new design and marveling over the nice new reinforced plastic that gave an air of quality and then hitting this holdup.

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Use thin, aluminium self adhesive foil. I did this in TT-02 and TT-02B and works perfect.

It is really shame, that Tamiya do such things. In my XV-01 which has hundred spacers stock, I can move rear diff from side to side.

IMG-20240216-090522582-HDR.jpg

TT-02 is cheap, but TD4 is like 3 or 4 times more expensive. I have not expected that.

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Well, trimming those tabs and flat-sanding the cover carefully eliminated about 50% of the slop. I'll try some of your suggestions to take up the rest. I was going to postulate the clearance issues might have been down to shrinkage rates or Tamiyas unfamiliarity with using these reinforced plastics with these types of designs (they certainly have used it elsewhere, TRF, DB01, etc. to great effect) but @skom25's example shows its a problem with run of the mill ABS/PC.

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There is certainly problem with some types of materials.

Stock TT-02B does not require anything at all. However, if you use GF parts, there is A LOT of play.

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