Pinion and Spur gear help please!!!

[branster36]

A few weeks ago i burned out my stock esc because i installed a hs-5245 onto the front of my crawler, now i just got into this crawling and this is my first rig so i went to my lhs and asked them about speed controls and new motors, i walked out of there with a castle creations brushless set up. so i went home got it all installed in the truck with the stock gearing and got it all set up. the first time i ran it i grabbed the throttle and the damn thing just took off, its really fast, but thats not what i want, i really want this thing to crawl. so my question to you guys whats the lowest possible gear ration i can run in this truck with out gear mesh issues?