You have 2 options. GPM make the gears in metal, so you can buy the full set including the internals which is expensive, or just the ring gear which is also expensive for a single gear but less so. RCJaz have the GPM gears

Or grab metal parts bag from the DF02 and the gear cases. This gives you enough to build 2 diffs for the price of a single GPM set. You need to file the pinion down a bit. I'm pretty sure its bag a, part 9400152, but you better check.

As a bonus the bag includes other bits like a 19T steel pinion which is a good match for a 13.5T and a bunch of those annoying self tappers Tamiya insist on using (I love Tamiya but wish they'd use proper hex head screws and bearings instead of bushings). Oh and another Tamiya hex wrench, you can never have enough of those.

I find that the metal gears slow the car considerably on the stock motor (have a couple TT02B's for my 5yo and his friends) but the 13.5T brushless setup like you suggested is the perfect match for the chassis and you don't notice the car being slower with metal gears on this setup.

The GPM gears (which I own..) are just the ring gears. Sadly.

So.. those gear sets, are the three gear sets, like in a TT01, so I'll need the TT01 casings to match that. STill, not a bad deal.

.................................. This is such a bad idea. But I really want this TT02b to work. hah.

Yep the DF02 gear set is the 3 gear so you need the cases

If you have the ring gear already...

https://www.rcjaz.co.nz/tamiya-tt02b-steel-propeller-shaft-gear-1pc-for-tt02-gpm-tt2100g2-p-90071612.html

thats the one you need right? There is also the complete set

https://www.rcjaz.co.nz/tamiya-tt02-steel-ring-gear-bevel-8pcs-set-for-tt02b-gpm-tt2100-p-90070804.html

you should see some of the builds on tamiyaclub, go nuts on the TT02, end up spending more than a TA07 /DB01 and they still won't perform as well. Fun though

any brands that produce hex screws for the tt02? i really dislike the philips. suggestions welcome!

Yeah Racing sells a Ti screw kit for like $14. I have used them in the past and they are decent for the money for sure

I end up buying bulk m3 machine screws off of ebay every so often. It's not a lot of money to get all the screws you might need.

Here's a decent deal on M3's and it's prime to.

I really recomend against buying stainless screws.

If you're gonna do it, do it right:
you'll need some countersunk too...
Really though, I go with ebay, and buy the exact kinds I need.

Stainless always goes "soft" and tears under load.

You have to to go with Tamiya 53792 if you want to use original Tamiya parts. 54515 will not fit TT-02 RR machine, they are too long.

Regards
Michael

Not necessary...
 

...Kit stuff works fine with the universals.
But you can upgrade the grub screw secured wheel axles with spring fixed ones. (Tamiya Part number 54623)

Michael