If you drive a pickup and it's 4WD then you will have a front and rear differential. The fluid should be changed every 30,000 to 50,000 miles and that depends on where you tow and the conditions that you drive in. It doesn't have to be changed as often as engine oil, but it's just as important to service it on a regular basis.
If you're wondering if you need to have your differentials serviced give us a call and we will check them for you and let you know.
Happy Adventures,
Heather