Motor vehicles rely on various fluids to function correctly, though people assume that’s only for components in the engine bay. Four-wheel drives and similar cars also rely on oil for their transfer cases, which plays a crucial role in their performance.
Transfer case oil needs changing every 50,000 kilometres driven, but you should do it more frequently if the vehicle is regularly carries or tows heavy loads. It’s vital to inspect the fluid if the transfer case has a leak, since it might be contaminated or there's not enough left.
This guide will walk you through how a transfer case works, why it needs transfer case oil, and what happens if the oil is contaminated or at low levels.
Let’s get started.
What Is a Transfer Case?
The best way to answer this is to start from the beginning - understanding what a transfer case is and how it works.
A transfer case is not as common to drivers as, say, the engine or transmission, because it's a drivetrain component found on 4x4 and AWD vehicles.
The transfer case has a very specific purpose, and that is to transfer power from the vehicle's transmission to its front and rear axles through the drive shaft.
As you can imagine, the transfer case has several moving metal parts inside that generate friction and heat.
For that reason, it needs transfer case oil to ensure the component can function correctly and remain useful for a long time.
What Type of Oil Goes into the Transfer Case?
Transfer cases typically rely on gear oil or automatic transmission fluid (ATF), but some makes and models depend on specialty lubricants.
If you're wondering which type of oil your vehicle requires, your first reference should be the car owner's manual. That document will specify the kinds of oils you should be using for optimal results.
Some car makers also make products tailor-made for their vehicle models. For example, you can find a Hilux transfer case oil made by Toyota.
Regardless of the kind of transfer case oil your vehicle uses or which brand you buy it from, they all serve similar purposes.
Transfer Case Oil Functions
This fluid provides:
- Lubrication: First and foremost, transfer case oil lubricates the many moving parts inside the transfer case. In other words, the oil reduces friction and ensures all components can move without damaging each other.
- Overheating prevention: Like other car fluids, transfer case oil prevents overheating. It absorbs heat from the moving gears, helping them stay within safe operating temperatures. On heavy-duty applications, a transfer case oil cooler might also be involved in providing additional cooling.
- Maximised lifespans: Overall, transfer case oil maximises the lifespan of the gears inside the case. Most of that comes from the lubricating and heat-absorbing properties of the oil. Moreover, it also prevents corrosion and delays general wear and tear.
As you can see, transfer case oil is a critical element in any vehicle with a transfer case. That’s especially true when those vehicles frequently move or tow heavy cargo, placing additional stress on their transfer cases.
That's why changing the transfer case oil must be a part of the vehicle's regular maintenance.
How Often Should You Change Transfer Case Oil?
As a rule, you should change your transfer case oil after driving 50,000 kilometres.
The process is straightforward and similar to other fluid replacements. First, you'll have to drain the fluid by removing the drain plug. Once done, replace the drain plug and remove the fill plug so you can begin pouring fresh transfer case oil.
Remember: 50,000 kilometres is just a ballpark figure. You’ll have to change the transfer case oil more often under the following circumstances:
- Heavy-duty usage: Some transfer cases experience more aggressive use than others. If you're regularly towing or carrying heavy loads, you'll want to check your transfer case oil's condition more frequently, perhaps even at the 25,000-kilometre mark.
- Transfer case oil leak: Like any other fluid, transfer case oil can leak. You must resolve the root cause of the leak before topping up or changing the transfer case oil. Some leaks can contaminate the oil, and if/when that happens, you’ll need to drain everything and refill it with fresh oil.
Staying on top of your transfer case oil changes is crucial to ensure everything works correctly for as long as possible. A fluid change might not seem like a big deal, but it significantly affects your transfer case’s condition and lifespan.
How Do I Know If My Transfer Case Needs Fluid?
The transfer case and its oil are out of your regular line of sight. You must rely on signs and symptoms to understand when the case might need a fluid top-up or change.
You’ll know your transfer case needs fluid when:
- Leaks: Always be mindful of puddles and marks on the ground underneath where you park. Those marks typically suggest you have a leak on board, potentially in the transfer case. After fixing the leak, you must top-up lost fluid or change the oil if contaminated.
- Rough gear changes: Inadequate transfer case fluid can cause transmission issues. Typically, that means difficulty changing gears or unexpectedly falling out of four-wheel-drive mode.
- Loud noises: Without enough fluid, moving parts don’t get lubricated, causing loud noises directly from the transfer case.
- Performance issues: The transfer case transfers power, so a lack of fluid can cause it to fail, leading to performance issues with the four-wheel-drive system.
When you notice one or more of these symptoms, you should get the vehicle checked immediately. But, again, there’s a significant possibility the root cause is in your transfer case.
Final Thoughts
When it comes to fluid changes, most people focus on engine bay components that require oils or lubricants. However, four-wheel-drive and all-wheel-drive vehicles also need oil for their transfer cases.
You should change your transfer case oil every 50,000 kilometres or sooner if your vehicle regularly carries heavy loads or there’s been a leak in the transfer case.
If you experience problems with your transfer case, the best thing to do is bring it to a professional for inspection. You can find the nearest workshops in your area using CarpartAU’s Directory. Get in touch with the pro immediately!
By Ray Hasbollah