Just thought id put in some tested numbers to anyone ending up.here by way of Google's blindness to post dates, and therefore making an old post relevant.
I have SEVEN variations of the ole' TT-02 cars.
I have three Trackstars in some. 7.5t(fast bash), 9.5t(drift), and 13.5t(rally/onroad bash).
If you build your diffz with some proper techniques you have absolutely NOTHING to worry about. If you need help there go check out nbTMM's post on TamiyaClub, (post topic title: TMM'sTMM's TT02 / TT02B Garage),
and you wont go wrong, you can also use tt01 gears and diff case but just using TMM's instructions will have you a solid set of diffs. I have had a Ruddog RP542 4.5t in one of my customized TT-02 cars for about 2 years now and no clicking, no breaking of gears, or parts....but to be fair it has CF shock mounts, spring steel CVDs, alloy center driveshaft or propellor shaft, etc.
When things break its an excuse to go shopping!
Anyway, i like the 13.5t TT-02 best. It has a Trackstar 80a Tirbo esc in it and its It's hell on wheels, plenty take off power, top end and runtime. i sawed off the top and bottom of the front hubs to get rid of the silly plastic bushing mounts, i cut it to within 0.5mm of the ball and then shimmed and placed titanium 0.45mm spacers and then screwed it down with tutanium screw, socket head top button head bottom. Then installed titanium beveled spacers mounted one each front and rear where the single screw goes in dead center of the lower bumper mount. This created a bump stop that shoots sparks just so sweetly, and the Aarms and bottom of hard chassis barely have road rash! The road has rash instead! This is great for badhing but maybe not racing...thats what a Down Stop Droop Plate is for!!!
I have an R1 Wurks 17.5t in another tt02, running hobbywing 10bl60 sensored or the older 60a sensored hobbywing esc the older model with the blue heatsink and the esc is square... the new 144001 brushless 45a esc is based on this and they look similar. Anyway she scootz and is fun but its just not the same as the 13.5t. i. I would not even enjoy racing it 17.5t blinky because its just not fun imo. i even tried a Skalar 21.5t and that was miserable...just so slow motion no matter how i geared it it just felt like i was driving a wet blanket!!! 7.5t uf you know what your doing when building the diffz, 13.5t if u dont but you at least follow TMM's build guide (especially about the diffz) and if you think them is to hot for u to handle go get you a a boxed combo TT-02 with the Torque 550 can motor and let it rip! 😉