Originally Posted by waitwhatsthat
I must be lucky because I have yet to break a diff. I'm running a 5250kv motor with a 12t pinion. All my diffs. Are filled with 7k diff oil. I only run on 2s though it's plenty fast. I do have some spare diffs and parts but haven't needed them yet. The only damage to the drivetrain is the drive cups are starting to wear pretty good.
Ditto here. 4250kv motor, 11t pinion, 40k oil in the center and 20k at each end. running on a pretty high traction clay track. Even with soft proline Ion tires, all 4 start slipping before the diff will strip. I feel like I have put as much stress on the gears as anyone, and I've never had a problem.
Some of us just got lucky and got good ones I guess.
To answer the question a couple posts up, the stock pinion is 14T, 3.125mm dia shaft, MOD1 pitch. So you have it right. I assume you're gearing it up, but if going down, 12t is really the smallest you can go. My 11t meshes pretty poorly, but it's as tight as the motor mount will allow.