How to Service a 4-Wheel Drive: Complete Guide

Servicing a 4-wheel drive is not like servicing a regular 2WD vehicle since there are more drivetrain and other 4WD components that require regular inspections and regreasing. 4-wheel drives have transfer cases, drive-shafts and other critical 4WD components that need to be attended to timeously. This article will discuss the various components that are unique to 4-wheel drives and what needs to be included with every service interval.

So, how do you service a 4-wheel drive? When servicing a 4-wheel drive you need to inspect all critical 4WD drivetrain components. This includes but not limited to differential, gearbox and transfer case fluids as well as driveshaft components like greasing the yokes, ball joints and U-joints. Inspecting all brake lines and electronic sensors underneath the 4WD is also vital when servicing a 4-wheel drive.

The next part of this article will discuss the various components in detail that needs to be inspected and serviced on any 4WD vehicle. We will look into why the drivetrain components need to be inspected as well as fluids and lastly how to reset the “service 4-wheel drive” light on the dash.

If you would like to read more about the ins and outs of servicing a 4-wheel drive, read on!

How to service a 4-wheel Drive: 4WD Components

When servicing a 4-wheel drive the initial phase of the service is just like any other vehicle. This means all vital lubrication, such as engine oil, oil filters, air filters, and fuel filters will be replaced as normal. If you have a petrol 4-wheel drive, you will need to inspect, clean and if necessary change plugs as well.

Next, you want to tackle all the electrical components of the 4-wheel drive, such as the electrical plugs, all sensors if it’s a modern 4WD as well as electrical wires for corrosion. These components need to be cleaned and sprayed with a dielectric spray on all the electrical contact points to ensure proper contact is made and the correct voltage is transferred.

This is vital since 4-wheel drives are used to drive in remote, challenging conditions that often involve deepwater submersions, long dusty gravel roads or exposure to ice and snow. All these off-road driving conditions have an impact on the performance of the 4-wheel drive in the long term since air and fuel filters get clogged quicker, moisture seeps into electrics sooner and drivetrain components lose lubrication faster.

Let’s next focus on the drivetrain components.

Drivetrain

Your drivetrain is situated below the vehicle and is the most vulnerable of all the 4-wheel drive components. Most of the drivetrain is exposed which means it takes quite a beating when driving off-road. The 4-wheel drive drivetrain consists of various movable joints and knuckles that needs to be thoroughly inspected. These include but not limited to:

  1. The U-joints on the front drive-shaft
  2. The U-joint on the rear drive-shafts
  3. The yoke needs to be re-lubricated
  4. Differential oil levels
  5. Transfer case oil levels
  6. Gearbox oil levels
  7. Transfer case actuator

All the above-mentioned components are unique to 4-wheel drive vehicles and require special attention before and after every major trip. At least an inspection is necessary.

Next, let’s look at the yoke and why it’s important to inspect and service it regularly.

Yoke

The yoke is positioned at the rear driveshaft as it meets the rear differential. It allows the vehicle suspension to flex and articulate without causing damage to the drive-shafts. The Yoke has a spline that slips into the rear driveshaft and is filled with grease for lubrication and protection from grime and moisture.

When you drive on dusty dirt roads the rear driveshaft is very exposed and usually takes a few knocks here and there when technical off-road driving takes place. The 4-wheel drive yoke needs to be inspected for off-road damage and play since this component can snap off clean if it runs dry. Once all the grease eventually runs out or you’ve been wading through rivers water regularly the old grease lubrication becomes ineffective and metal fatigue sets in which could result in component failure.

Transfer Case fluid

This fluid needs to be inspected for metal filings with every major service. This is a high torque component since all the engine power and torque is transferred through this component and through the drivetrain to the front and rear axles. A 4-wheel drive transmission case oil levels need to be checked and if the oil level is too high, with excess oil oozing out, it should raise alarm bells.

This means you could have a leak in the seal between the transmission box and the transfer case. This needs to be attended to as a matter of urgency and I would recommend not engaging in any 4-wheel driving until this has been resolved.

Gearbox Fluid

Another high-stress component is the gearbox. If you have an automatic gearbox the gearbox oil is of utmost importance to maintain and levels to be regularly checked. The oil inside the auto gearbox is designed to lubricate and also reduce heat build-up inside the gearbox. Your auto gearbox oil cooler also needs regular inspection. Check for leaks and metal filings in oil which could indicate metal friction and severe ware inside the gearbox

Actuator Switch

The actuator switch is an electrical switch with a shaft that is positioned below the 4-wheel drive on the transfer case. The function of the switch is to engage the 4-wheel drive hi and lo when the dial is selected in the cabin. The actuator does the job of the older short ration gear-lever positioned next to the main gear shift stick.

Due to its position under the vehicle, it is also very exposed and vulnerable to the elements off-road. Remove the switch connections, clean and spray with a dielectric spray.

Brake Lines

Brake lines of most vehicles run along the bottom of the chassis of the vehicle. A 4-wheel drive is no different. This means it’s also another vulnerable component of a 4-wheel drive. Always inspect the lines for damage and leaks. Make sure all the brake lines are still properly secured under the chassis since any off-road obstacle like a bush or dry branch could get caught in there and rip it lose.

Diff-locker

The diff-locker is usually positioned on the rear diff but some 4-wheel drives have a front differential locker as well. The purpose of the diff locker is to lock the wheel axle to rotate as one single unit when off-roading on challenging low-traction terrains. This should only be used in circumstances where traction is low and where wheel slippage is a strong possibility.

Failure to engage the rear locker at the appropriate time could result in damage to the drivetrain and tires and could cause drivetrain binding. More about that here.

The diff locker should be tested for functionality and also cleaned and sprayed with a dielectric spray to maintain its electrical connection.

Diff fluid

Differential fluids are vital since they lubricate the gears inside the diff. the oil needs to be changed at least every 35000 miles. Always consult the owner’s manual for the correct grade of differential oil to be used. Check oil levels and top-up if necessary.

Change the rear diff oils on your 4-wheel drive every 15,000 miles but not more than 36,000 miles. Always refer to your owner’s manual to make sure you use the correct lubricants in the diffs. If your 4Wd has a lockable differential and you use the wrong lubricant, this could mean damage to the diff or locking mechanism failure to activate.

U-joints

U-joints are what in most cases allows the 4-wheel drive to flex and articulate. They are a perishable component and should be checked every so often for leaks in the rubber seals and ensure proper lubrication. Check for dripping rust water or cracked seals which will indicate its time to replace.

A loud popping sound is usually associated with a damaged or dry u-joint. You can read more about that here

Almost all u-joints are serviceable and have a greaseable nipple on the side of the U-joint. This allows you to insert more grease into the four tiny housings where little metal pins are located. These low hanging components can easily catch a rock and get damaged off-road so inspect for damage before and after each off-road trip. In the event that the nipple gets damaged, all the grease could escape and result in component failure shortly thereafter.

Reset 4-Wheel drive service light

For directions on how to reset the service light, check your owner’s manual for the correct steps. Each 4-wheel drive manufacturer has their own method of doing this.


Below is a short video demonstrating how to reset a VW Amarok’s service light.

Conclusion

How to service a 4 wheel drive

Look after your 4-wheel drive and it will look after you. Do the due diligence to inspect the various components listed above since that will give you peace of mind every time you venture into the unknown.

If you don’t do the service yourself, never take it for granted the service technician did all the necessary inspections. Get underneath the 4-wheel drive and check for yourself that all the vital components have been serviced. Even if it’s just for your own sanity.

A 4-wheel drive has many more components than a normal 2WD vehicle and this requires careful attention to ensure your 4WD remains reliable and brings you back home safely every time.

Jade C.

4-Wheel drives and off-road driving techniques has been my passion for over 20 years. Here we strive to provide the most accurate, up-to-date, information about the functionality, common faults and latest technology built into most 4 Wheel Drives.

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