Differentials deliver the power from the transmission to wheels. Extreme high operating temperatures can cause thermal breakdown of the differential fluid, leading to a loss of lubrication and deposit formation. This can cause gears to grind while leaving behind metal shavings and other debris. Most vehicles featuring four-wheel drive have three gearboxes. These include the front differential, rear differential, and transfer case. Consult your owner’s manual for appropriate mileage intervals for service.