How fast can this setup go
 

I have a tc3 that's been sitting collecting dust for years. I pulled it out and decided to put some electronics in it. The setup is castle 5700 kv motor with mmp esc and I want to run it on 3s. I have a 26 pinion and not sure on the spur but it's probably stock. If I wanted to gear it to see how fast it will go about how fast am I looking at with this setup?

I dont think you will have any problem going VERY VERY fast, but putting the power to the ground without losing traction, i dont know, but i think its gonna be a handful. if you are just drag racing it will do fine, but if you want to race in a track, i dont think you can get the car to grip.

I have never had an on road car. Bought this thing like 7 years ago and it's been sitting. It still looks new. I just want to see how fast I can get it. I may do some on road track driving on carpet but will just run it on 2s and turn the power down. So is it possible this thing will hit 70?

i have no experience with your ESC and the motor, so i cant tell you how fast it will go. I am using a HW 120A V2.1 with a Team Powers 10.5T motor, with boost and turbo on up to 50 degrees, my car is as fast as a nitro car on the straights, perhaps even faster, and i am driving a car that is as old as the tc3, from 2001. If your esc has boost and timing, then you will go very very fast. The trick with a shaft car is to accelarate gently, so set your punch to the lowest. I think you shouldnt concern yourself about top speed only, without control, speed is nothing, beleive me i have been there, struggling to get my car to grip at the rear under braking and punching out of corners, now that i have the grip, i can really go all out.
as for 70mph, i dont think so, perhaps 70kmh...

So you think only 44? Seems low. My slash with the same setup on 2s with the esc tuned to 75 percent power would run that fast. I guess I need a radar gun.

if you go to gearchart.com you can estimate your top speed by inputting the required values.
Hope that helps.

With that setup on 3s lipo 70MPH is very doable. I had a tc4 with the losi 6400 setup on 3s and went 88 on a police radar gun before it went over backwards. Just make sure when you mount your body that the nose is all the way up against the foam bumper and put a brace under the hood and roof so that it will not colapse from the immense downforce you will be generating. As for racing it on a track and not just making speed runs 17.5 is the biggest brushless motor I would try to run becuase it will just make the car dance around and have very unusual charicteristics because a shaft drive has so much snap where as a belt drive car gives more. Your sensorless syetem is great for speed but not racing because it is not as precise becaause the esc is not 100% sure where the rotor is so you lose that midrange feel but you gain some efficency becuase there is electronics to power. But for speed purposes you have a good set up and for racing I would invest in a tekin RS speed control and a Duo 3 motor. I say that because it is the smoothest motor out there right now. I've run LRP, Speed passion, Duo, Orion, among others and it is the smoothest to drive in the infield and is still plenty fast for racing in stock or boosted classes. Just my 2 cents though