Just bought a e-maxx

I just bought a e-maxx off a guy yesterday. It came with a brand new hv-maxx system with 4 pack of 3600 smc pro matched cells. The truck was never driven on dirt, so its like brand new, not even a speck of dirt on the entire truck. My question is though, he has it geared at 66 spur, 17 pinion, would this cause alot of overheating, or would it dramatically reduce my top speed? Thanks