Locking the diffs will put extra strain on the drivetrain, and therefore the motor. A standard motor will struggle in loose gravel. The teu-101bk esc can easily handle a Tamiya Sport Tuned motor, so throw that in. If you want more drive to the wheels in the gravel, put the bevel gears in the rear, and a ball diff in the front. t can take either the Manta Ray diff, or another one I can't remembe off-hand.