A drive system for a vehicle having a rear drive assembly powered by a first power source, a front drive assembly in selective electrical communication with a second power source, a selector switch to selectively permit or prevent electrical communication between the front drive assembly and the second power source, and an output capacity sensor to detect an output of the first power source, where the rear drive assembly drives the vehicle when the selector switch is in a first position and both the rear and front drive assemblies drive the vehicle when the selector switch is in a second position and the output capacity sensor detects that the output of the first power source meets a threshold output.