step1
step2
step3
step4
step5
step6
step7
8.replace the gear box
a.Per the above step ,unlock the screws
b.disconnect the plug of the battery and gear box
c.disconnect the battery wire.the disassemble the driving wheel and rear wheel ,then pull out the rear axle
d.unlock the screws of the grey plastic box ,then open it to get the gear box
