The gearbox refers to differentials, final drives, manual transmissions and transfer cases, and gearbox service on each of these is important. Each of these gearbox types requires a specific fluid for proper lubrication. Gearbox fluid protects these drive train parts and components against damage from heat and contaminants by lubricating gears, shafts and bearings.
Like any fluid, Gearbox Fluid breaks down over time and loses its ability to lubricate and protect vital drive train components. Gearbox Fluid Service includes draining of the old fluid, inspection of the drain plugs, and a fill with new Gearbox Fluid.
Refer to your vehicle owner’s manual for recommended service intervals.