Components That Require Oil and Fluid
Heavy-Duty Engine and Transmission
Your engine and transmission both need oil and fluid to adequately ease friction and eliminate heat. Your engine needs its oil changed every 20 thousand miles, whereas your transmission needs its fluid changed once every 30 to 60 thousand miles. The difference between the two service intervals is due to your engine having an internal combustion chamber, meaning its fluid gets significantly hotter. Outside of lubrication, your engine also needs its coolant changed once every 30 to 60 thousand miles.
Light-duty trucks that have multiple drive modes need the fluid in their transfer case changed out once every 30 to 60 thousand miles as well. Most manufacturers recommend changing this fluid at the same time as your transmission fluid. One important thing to note here is that you should thoroughly run through your different drive modes at least once a month to prevent transfer case fluid from breaking down.
Your differentials are responsible for diverting power towards multiple wheels. Since they have moving gears within them, changing their fluid on a regular basis is a must. Do keep in mind that your differentials share fluid with your axles, for they’re within one housing. This means that if one leaks, both are affected.