Power Truck disassemby

Hello everyone, I am new to this forum so please bear with me. I have a Tyco Rock Island Line locomotive that the motor runs but the loco won't move. It was running fine until yesterday when it just stopped dead on it's tracks! I am sure one of the gears is bad and am trying to take the power truck apart. I got the truck out of the shell but can't figure out how to finish the disassembly. I have attached a photo of the truck to help. Any assistance is appreciated.