The TC4 was a decent RTR car when sold and from my own personal racing experience, the TC4 was less capable than the TC3. I recall these were selling for under $100 USD when they came out and also came fully built. They only ever sold these as a chassis, never with tires, rims and a body.

The weak point with the TC4 is the steering belcranks, and they will break and often. You can replace these with after market alloy, but those will break as well. Poor design.

The drive train is not the same as the TC3 and parts don't exchange between them. Yes, they are both shaft drive with inline motors but the similarity ends there. The suspension is different as well.

I raced a TC4 in the Canadian VTA class where we were limited to a 25.5 brushless motor and the car ran great in this class. It helped to make a wider bumper to reduce the steering belcrank breakage somewhat.

Parts these days are scarce, so if you plan to race a TC4 you'd best stock up on all the parts you can find. Probably best to buy complete rollers / sliders if you can to save a few bucks.