Original front ball diff? 23T brushed or 4000kv brushless would be the "max".
If you want more speed, you need the front direct solid, only HK$120, but run forever. Then you can "think" about 5.5, 4.5 brushless.
I never know the original TA05 (no modification) can support the 10T motor.
Meanwhile, what mean by 'Original front ball diff' and 'front direct solid'? I'm a new comer.
Thanks!