10xl 16 cells gearing
 

i hope this setup will be a little more for giving on temps and runtime, its going in a extended e- maxx, just for fun, what gearing does everybody recommend i only have a 18t pinion spur 66-72.

not breaking speed records, just hills and tall grass normal conditions

I would go with the 66T spur. You might even want to pick up a 64T spur, I know it's not much but every little bit helps. I have a custom converted LST2 with a second gear only E-Maxx tranny, 9XL on 4s Lipo and I am running 22T pinion on 66T spur. I also run a 40mm fan and temps never have gotten over 135F so far.