Four-wheel drive (4WD) and all-wheel drive (AWD) may operate differently but the theory is still the same. 4WD vehicles are generally a part-time system. They operate as rear-wheel drive until a switch or lever is activated, allowing the transfer case to “transfer” some of the power to the front wheels. AWD is typically a permanent four-wheel drive system, always engaged. Through the use of various sensors, AWD will vary the power split front and rear automatically. Both systems still use a transfer case to split the power to the front and rear. Transfer case fluid level and condition are vital to the longevity and proper operation of your 4WD and AWD systems.
Part 1 of 2: Draining the transfer case
Transfer case fluid - consult your owner’s manual for the correct fluid type and quantity
Wrenches - open/box end
Note: Since the majority of pickup trucks and SUVs have enough ground clearance, you generally will not need to lift the vehicle. If, however, your vehicle does not have enough clearance for you to lay underneath it, follow proper jacking instructions for your vehicle. Even if you must lift your vehicle, it must be level when refilling the fluid.
Step 1: Prepare the vehicle. Make certain the vehicle has cooled for at least 2 hours as to not handle hot fluids. Set the parking brake and chock/block at least one wheel front and back.
Step 2: Drain the fluid. The drain and fill plugs are generally located facing the rear of the transfer case and vehicle.
The lower plug is the drain and the plug located higher up is the fill. Remove the fill plug, then remove the drain plug. Allow the fluid to drain as long as possible as to extract the maximum amount.
Part 2 of 2: Refilling the transfer case
Step 1: Reinstall the drain plug. Once the fluid has drained completely, reinstall the drain plug, leaving the fill plug out.
- Tip: Some fluid bottles come with a spout top so you can squeeze the fluid out through it. If there is not enough room under your vehicle to get it into the fill plug, the filler/extraction syringe listed in the materials needed will come in handy.
Step 2: Refill the transfer case. The transfer case does not have a dipstick to check fluid level. It is basically “fill till you spill.” Using either the fluid bottle top or syringe, fill the fluid into the filler plug hole until fluid runs out of it.
Step 3: Clean up. Reinstall the fluid fill plug. Wipe any excess fluid from the transfer case. Dispose of the use fluid properly. In most cases, your local auto parts store will take used oil/fluids and recycle them free of charge.
If your four wheel or all-wheel drive vehicle is due for a transfer case service, contact YourMechanic today to arrange for a mobile technician to come to your home or office.
This article originally appeared on YourMechanic.com as How to Replace Transfer Case Fluid and was authored by Ronny Brown.