Unless you are racing, I'd stay away from the FT model. They do break more easily. As for the tranny, I won't say it's bullet proof, but it's pretty close. Just check and rebuild the diff on a regular basis. I used to run a MM7700 system in my T4 on 3S lipo and it was down right sick. It would eat Jato 3.3s like dessert. The 5700 on 3S is going to be similar. I just got out of it because the T4 on a whole wasn't strong enough to run the Castle system. I didn't have any trouble with the tranny, but other parts. Even hitting an expansion joint at 60+ mph can be catastrophic. The FT would be even worse.