How to Change Transfer Case Fluid

Learning how to change transfer case fluid is a must if you own an automobile with a four-wheel drive (4WD) or all-wheel drive (AWD) system. It can prevent significant repairs and save you considerable cash over the long term. More importantly, it’s the key to ensuring your workhorse of a sedan, hatchback, sport utility vehicle, crossover, pickup truck or van delivers the kind of performance you expect from it, whatever you haul or tow and wherever you go.

What Is Transfer Case Fluid?

This fluid is a substance that lubricates and cools the transfer case. This component has one job — transmit engine torque from the transmission via the drivetrain to the correct set of four wheels through the front and rear axles based on your vehicle’s mode.

If you have a full-time 4WD system, the transfer case distributes equal force across all wheels. Your vehicle’s center differential locks the front and rear driveshafts upon engagement, allowing them to move at the same speed.

If you have a part-time 4WD system, the transfer case splits engine power between the front and rear axles when you switch from two- to four-wheel.

If you have an automatic 4WD system, the transfer case kicks in when your vehicle switches itself from two- to four-wheel after detecting that the road conditions require more traction.

If you have an AWD system, the transfer case always delivers torque to all wheels but sends more power to those your vehicle’s computer system thinks need it most on the fly.

A transfer case’s inner workings are subject to constant friction and extreme heat. Its fluid greases the gears and bearings, coating them to mitigate metal-on-metal contact and prevent premature wear and tear.

Moreover, the liquid keeps the transfer case’s temperature levels low. It absorbs heat from the moving parts upon contact, leaving them cooler after lubricating them.

Plus, this fluid helps remove pollutants from gears and bearings. Metal particles and other debris may contaminate your vehicle’s transfer case and wreak havoc on its gearwork.

Transfer case fluid drenches your vehicle’s wet clutch if you drive a stick shift. This lubricant is usually thicker than a typical fluid and gives off a distinct odor due to its sulfur-based compounds.

What Kind of Fluid Goes in a Transfer Case?

Transfer cases have a specially formulated fluid dedicated to them. It’s the go-to transfer case lubricant for multi-axle vehicles. However, many car owners use automatic transmission fluid without experiencing any problems.

If you have an older set of wheels, you may use gear oil. Some refer to it as transfer case oil to distinguish it from other vehicle fluids.

Check your owner’s manual to know what product your car manufacturer recommends. Putting the wrong fluid in the transfer case results in poor lubrication, overheating and mechanical problems.

Low Transfer Case Fluid Symptoms

Vehicle fluids don’t just disappear — they must have gone somewhere to be running low. Unknown leakage can cause your transfer case’s fluid to run low, causing a vicious cycle resulting in mechanical failure.

Inadequate lubrication makes the cogs in this gearbox more prone to friction-related damage due to physical contact and constant movement. Increased abrasion produces more debris in the transfer case, resulting in a higher risk of contamination. High temperatures are another cause for concern.

Look for the following symptoms when you run low on transfer case fluid.

Spotting a Transfer Case Fluid Leak

Transfer case fluid leaves a trail of grease when it leaks. The liquid may come out when the bolts securing the vibration damper have loosened, increasing the chances of the drain plug detaching due to nonstop rattling.

Check your owner’s manual to locate the transfer case fluid on your vehicle. It can be confusing when you’ve never seen your car’s underside. Typically, you can find it at the rear of the gearbox connected to the engine and in front of the rear driveshaft. It’s rather bulky because it houses gears and bearings.

Seeing the AWD or 4WD Warning Light On

The AWD or 4WD warning light may come alive when your car senses your transfer case is running out of juice. If you drive a 4WD vehicle, it may have unique dashboard indicators and an airbag warning light near the shift gearbox for easy disengagement to prevent accidental deployment when driving off-road.

4WD warning lights appear in various designs to make things even more confusing. You may see an axle with glowing wheels, a glowing axle, “4×4” or the initials 4WD.

Any of these indicators suggest that your transfer case is overheating, which may be due to a dangerously low fluid level. Investigate the problem sooner rather than later to diagnose and address it accordingly.

Hearing Grinding Noises

Strange sounds can be a cry for help from a poorly oiled transfer case. These noises may come from components that have seen better days after directly coming into contact with one another. Replacing bad gears and bearings can’t solve the problem without refilling the transfer case with new fluid.

Smelling Something Burning

The high amount of friction exudes a burnt odor — another proof that your transfer case is almost dry inside.

Struggling to Shift Gears

Finding it challenging to move from lower to higher gears, and vice versa, is a sign that your transfer case is shot. Loss of fluid is a likely culprit. Your transfer case’s moving parts are prone to slippage when there isn’t sufficient lubrication.

Experiencing 4WD Engagement or Disengagement Delays

Switching into and out of 4WD mode should be a breeze when every gear and bearing in the transfer case is in good condition. Encountering jerks when distributing engine torque throughout the four wheels can be evidence of worn-out parts — a sign that your transfer case fluid is almost gone.

How to Check Transfer Case Fluid Level

You should check the fluid level in your transfer case whenever you suspect it’s running out of lubricant.

Locate and loosen your transfer case’s fill bolt. Remove it entirely by hand. If you have enough liquid, it should be level with the fill hole or slightly dribble out. Otherwise, you need to fill your transfer case with fluid to capacity.

Do You Need to Change Fluids When Your Transfer Case Is Full?

Say your transfer case is full. You may still need to replace its fluid when its quality has diminished. Transfer case fluids don’t lubricate well forever. They contain various additives designed to prevent rust, inhibit frothing, keep contaminants harmless by capturing and suspending them and more. These chemicals degrade and lose their effectiveness over time.

Unlike windshield wiper fluid which you may have to change monthly, transfer case fluids can last longer. Use your owner’s manual to determine how frequently you should flush out this gearbox.

How to Change Transfer Case Fluid

The professional cost of a transfer case fluid change isn’t worth it if it’s the only reason you bring your car to the mechanic. Do it at home instead — the only tools you need are wheel chocks, car jack, jack stands, ratchet, fluid pump and collection pan. Follow these steps to change your transfer case fluid.

Immobilize Your Parked Car

Pull the emergency or hand brake to lock your wheels in place and keep your vehicle motionless. Then, chock off the rear wheels. You can use bricks if you don’t have wheel chocks.

Lift Your Car

Slide the jack under the front of your car. Place it under the crossmember — your vehicle’s main structural component — to support your car’s weight as you jack it up as high as possible to change fluids comfortably.

Grab two jack stands and place them under the frame rails — large metal pieces running from the front to the back of your vehicle. Slowly lower the jack onto the stands. Remove the jack from the front and do the back.

Lift from the rear differential — the bulky piece of metal connected to the rear drive axles. Place the jack under the rear differential’s center to keep it from sliding off. Monitor the front jack stands to ensure they don’t tilt as you lift.

Once your vehicle’s rear is high enough, look for thick, sturdy pieces of metal, like subframes, under which you can put the stands. Slowly lower the jack until the stands touch your vehicle.

Locate Your Transfer Case’s Fill and Drain Plugs

Consult your owner’s manual if you can’t find your transfer case. If you know where it is, slide under it and spot the fill and drain plugs. The former is usually higher than the latter. A vibration damper covers the drain plug, keeping it from vibrating out as your vehicle moves.

Remove the Bolts

Use your ratchet to remove the remove your fill plug. Then, uninstall the bolts fastening the vibration damper to reveal the drain plug behind it.

Let the Old Fluid Flow Out

Once the drain plug is visible, place a collection pan — similar to something you would use when flushing out an old engine coolant — under it. Loosen the bolt and remove it by hand. The liquid should gush out of the hole and empty the transfer case quickly.

Cover the Drain Plug

Reinstall the bolt by hand, and tighten it with a ratchet.

Pump in the New Fluid

Grab your chosen transfer case fluid. Insert your fluid pump’s short suction tube into the transfer case and the longer one into the fill hole. Begin hand-pumping the new fluid into your transfer case until it reaches full capacity or the liquid starts coming out.

Reinstall All the Other Bolts

Screw in your fill plug by hand, and tighten it with the ratchet. Do the same for each of your vibration damper’s bolts, except apply a dab of medium-strength threadlocker to them first.

How Not to Change Transfer Case Fluid — 7 Worst Mistakes

Although changing the transfer case fluid is straightforward, committing a single error can be perilous. Avoid these seven cardinal mistakes when changing your transfer case fluid.

1. Slide Underneath a Wobbly Car

Successfully lifting your vehicle doesn’t guarantee it will remain elevated while you’re under it. Shake it to ensure it’s steady before putting your body on the line. Consider leaving the car jack under the rear differential and placing ramps underneath the front wheels to provide a secondary layer of protection if any stand fails.

2. Forgetting to Ensure Your Vehicle Is Level

Use a magnetic level to determine whether your suspended vehicle is even before unscrewing the bolts. Your car should be level to fill fluid into the transfer case to capacity and avoid premature leakage.

3. Removing the Drain Bolt Before the Fill Bolt

Always uninstall the fill plug before the drain plug. Failing to unscrew the fill hole’s bolt after draining the old fluid would empty the transfer case. Old fluid is better than no fluid. Driving without any sort of lubrication may damage your vehicle’s moving parts.

4. Wearing No Protective Gear

Exposing yourself to transfer case fluid isn’t as dangerous as handling lead-acid batteries. While gloves, long-sleeved shirts and safety glasses are optional, wearing personal protective equipment can safeguard you against toxic chemicals.

5. Refilling With a Wrong Liquid

Transfer case fluids share similarities with some liquids used in automotive. However, they aren’t necessarily interchangeable, so don’t use one when you should use another.

Read the fluid container’s level closely to ensure you have a suitable liquid for your transfer case and avoid massive headaches down the road.

6. Tightening Bolts Too Much

Overdoing this part can strip out the threads, causing bolts to unfasten when driving. Tighten them to the point where you can’t unscrew them with your hands, but you should be able to remove them easily with a hand tool.

7. Skipping Threadlocker Application

A medium-strength threadlocker glues the bolts into the threads, helping prevent them from vibrating out while you’re on the road. Otherwise, the vibration damper might come off without warning, increasing the chances of a transfer case fluid leak.

Change Your Transfer Case Fluid With Caution

Learning how to change transfer case fluid is as easy as 1-2-3 when you familiarize yourself with other essential car maintenance tasks. While it may be simple, its dangers are real and can be severe. Observe safety to keep your 4WD or AWD vehicle — and yourself — strong and healthy.