DIFFERENTIALS
Besides 4 × 4s, cars with rear-wheel drive and all-wheel drive have differentials
as part of the drivetrain system. There’s not a whole lot to do to these except
check the fluid level at every oil change. The technician should check the gear
lubricant for proper level, color, and consistency. Low lubricant level indicates a
leak, a milky color indicates moisture in the lubricant, and the presence of metal
in the lubricant indicates mechanical wear. Check your owner’s manual for the
recommended fluid change intervals.