Most SUVs available today are car-based crossover models, so they aren't intended for off-road driving, but they can be used for towing, in dusty or muddy conditions, heavy stop-and-go driving and other such conditions that qualify as severe. In those cases, you might need to change the transfer case and differential oil periodically instead of just having it inspected. If you drive any vehicle for extended periods under severe conditions, you should perform other routine maintenance items more often, such as oil and transmission-fluid changes, so that isn't unique to all-wheel- and four-wheel-drive vehicles.
For example, Hyundai says to inspect the propeller shaft (also known as the drive shaft), transfer case oil and rear axle oil on all-wheel-drive versions of the 2013 Santa Fe Sport every 15,000 miles or annually under normal driving conditions. For severe conditions, Hyundai says to inspect both every 7,500 miles and replace them at five years or 75,000 miles, or after they were submerged in water.
On the all-wheel-drive Chevrolet Equinox and Traverse crossovers, the automaker recommends changing the transfer case fluid at 97,500 miles for normal driving and every 45,000 miles for severe conditions. That is the only additional maintenance listed for all-wheel-drive models compared to front-wheel-drive versions.
Chevrolet recommends the same schedule for the off-road-capable four-wheel-drive Suburban and Tahoe SUVs, though it also suggests checking the fluid level in the transfer case periodically (without specifying how often). Otherwise, Chevrolet says the four-wheel-drive system requires no additional maintenance unless it produces unusual noises or performance deteriorates.
Because maintenance recommendations vary by manufacturer, it is best to consult the maintenance schedule for your vehicle. The biggest variable is how the vehicle is used, so check to see if your driving qualifies as severe.Related