gas can't freeze
-direct to diff conversions have no flexibility in gearing and shouldn't be considered unless you understand all of brushless r/c's parameters
- we can't say until we know you're spur/pinion and diff gearing, kv of your motor, tire size and desired top speed
-BrianG's website
http://www.scriptasylum.com/rc_speed/_wiring.html located in sticky in the brushless section titled, "speed calculator"
you should read the stickies in the brushless section and any faq's and you will be well on your way