i had a tt01 previous to my yokomo bd.i put a alloy engine mount in to replace the factory plastic one.i had a 23 turn atlas motor,heaps of torque.great for drifting.alloy steering gave it some more turn.dont get to carried away with alloy arms etc as these tend to bend(more than plastic)plastic ones are cheaper to replace as well.the diff can be found if you open up the gearboxs(located at each end of the chassis.once you have the gearbox open,the diff will be sitting in the middle.a big gear wheel with a housing on one side of it.take it out,open it up.pack it full of bluetac and close it up and chuck it back in.thats a locked diff.i found locking the front diff got my tt01 turning sideways real well.get some good pvc(plastic) tires and youll be sliding all over the show in no time.
hope this helps