My Jammin CRT pix

[glassdoctor]

You can't talk gearing without telling what motor and battery you have?

4s? What motor wind?

My CRT is just like yours, with MM, 4s lipos and a 1515 1700kv... and it does very well geared 12/52. I did put a fan over the motor/esc to lower temps but it was still ok without fans.

I assume you have a higher kv motor like the 2200... so the gearing would be different of course. But it doesn't matter where you change the gearing... diffs or spur/pinion. The overall ratio is all that matters.