609E Rock Crawler Upgrade

Found this 609E Rock Crawler on amazon for $50. I took this project on for my 4 year old. Sturgill wanted a large RC "monster truck", but the cost of a decent one was out of the question since he's so young. Straight out of the box the gears in the servo were grinding noisily. Had very limited range of steering as well. That's where I began the process of putting in a new servo. Basically the cheap esc that was in it, wouldn't take the new servo plug, so I had to upgrade the rest of the electronics inside.
Each motor needs its own esc. to do this, I connected both the brushed 20a mini esc power wires ( black and a red) straight to the battery's negative and positive wires. Then took the female motor connectors from the old esc board and soldered them to each mini esc. A "y" cable will allow both motors to plug in the channel corresponding to the throttle. (in my case channel 2). To get the lights to plug into the new receiver, I had to sacrifice one end of an extra "y" cable, and connected the red and the white wires of the light to the red and the white wires of the new cable. (leaving a black wire on the new cable that connects to nothing).
The servo was a different story. Had to grind some plastic. I used a torch lighter to heat up some places to help mold a nice place for it. The servo horn had to be cut as well as drilling a new hole for the linkage to fasten to. Hope this can help somehow!

[@green_life7]

What specifications are the original tyre axle motors?
Are they powerful enough to be upgraded to 11.1 volt instead of 7.4 volt?