The drivetrain consists of transmission, clutch, yokes, drivelines, hanger bearings and differentials. All these pieces make up your drivetrain and it is what converts power that your engine makes into force to apply to the wheels also known as torque. Without these complex gear systems in transmissions and differentials it would be really hard to pull tens of thousands of pounds on a flat road let alone uphill. The gear oil used in transmissions and differentials is crucial, it always needs to be maintained at the correct level and viscosity. If you wait to long in between fluid replacements the oil will become thin and cause the gears to grind against each other wearing them down which will then lead to yet another unwanted breakdown on the road. To prevent towing bills and roadside breakdowns these components need to be checked at every preventative maintenance inspection.