The SCX10 is capable of a pretty wide range of gear ratios just by changing the spur and pinion gears. It will go from a 73.85:1 to 15.38:1. It all depends on what you really want to do with it. If you want to "race" around the back yard it won't be that great of a crawler and vise verse. UNLESS you are ready to drop some money on a 'want a summit' transmission holder, a summit 2 speed transmission, a new speed controller/motor combo and a higher voltage battery.
Again, RCCrawler.com will have a ton more info that will answer many of your questions.
Originally Posted by walldk
Step away from from the vehicle and seek professional help.