If an all-wheel drive vehicle recently entered your life, there are different maintenance issues compared to a conventional car or truck an owner should be aware of such as the front differential. Regular checks of and changing the fluid in differentials are strongly advised; in some cases, at no more than 48,000 to 57,600 kilometers. And it could be as frequently as every 38,000 kilometers. Make it a point to look under the vehicle for any types of leaks.
Behind the differentials is the transfer case, which allots power either to the front wheels, rear wheels, or all of the wheels. It also requires periodic service. Fluid levels must be examined. If during the inspection fluid has run out of the transfer case, that’s a sign of overfilling that might indicate a faulty seal in the rear of the transmission allowing fluid into the transfer case. When you check the fluid level in the transfer case, if a lot of fluid runs out as if it’s overfilled, well it probably is overfilled. And that’s probably because there’s a bad seal in the back of the transmission and transmission fluid is entering the transfer case. Have this attended to soon, otherwise repair costs could mushroom.
The motor on the transfer case shifts it through the gears. Since it’s exposed and has an electrical connector, at least once per year open the connector and coat it with di-electric grease to discourage internal corrosion.
Fluid must be changed regularly in the rear differential. That could be at 24,000 kilometers but usually at not more than 57,600 kilometers, and must be kept up regularly. Ensure the right lubricant is used, because most are locking differentials. The wrong lubricant may prevent the locking mechanism from functioning.
Self-leveling systems on SUVs and trucks require maintenance as well. They sense the vehicle’s height and switch on the air pump to maintain equilibrium, and they in turn rely on mechanical linkages for levelling. Avoid premature failure by lubricating when required.
Further information is available at: http://www.motorweek.org/features/goss_garage/4wd_maintenance