Sounds like you're saying with NO LOAD the system works (i.e. wheels in the air) on the ground it stutters. It's already been said once, you've got too much draw on that battery. Does it feel hot? Definitely try a 7-cell Nimh or a 2S Lipo. Honestly you'll want to go LIPO. Also, did you go through the ESC setup using your controller? Did you configure the cutoff voltages and punch/timing? Well I would try a different type of battery before panicking too much.