Blog Car Care Advice 7 Reasons Why the 4-Wheel Drive Won’t Disengage + 6 Fixes
Car Care Advice

7 Reasons Why the 4-Wheel Drive Won’t Disengage + 6 Fixes

Looking for a mechanic near you for maintenance or repair? AutoNation Mobile Service brings the shop to you. Get a free instant quote today.
Get a Quote

It can be incredibly frustrating for seasoned off-road enthusiasts and novices alike when the 4-wheel drive won’t disengage. This can be especially true since you shouldn’t use the 4WD system on dry pavement. 

However, if you find yourself in this situation, don’t panic. 

We’ll dive into why the 4-wheel drive won’t disengage, some solutions, how to prevent unnecessary wear and tear, and more. 

This Article Contains:

Let’s get started.

7 Reasons Why the 4-Wheel Drive Won’t Disengage

In the world of 4-wheel drive vehicles, sometimes the hubs don’t want to disengage. 
Here are seven reasons why:

1. Defective Selector Switch 

The selector switch or the 4WD button controls the two-wheel drive and four-wheel drive. If the wires to the selector switch are defective, it could cause an electrical connection issue and prevent it from switching out of 4WD.

If there are no other symptoms, a faulty 4WD button or the wires may be the reason. In this case, the best thing to do is call a mechanic.

2. A Faulty Actuator or Actuator Motor

The actuator moves the shift fork, which engages and disengages the front axle. The selector switch signals the actuator motor to move the shift fork. 

However, if the actuator is faulty, it may not be able to engage or disengage the system properly. The actuator can fail through wear and tear, corrosion, or overheating. Similarly, an actuator motor is also susceptible to mechanical failures.

3. Seized Differential

The differential, or just diff, allows each wheel to turn at different speeds on the axle. Without the diff, the inside wheels would drag when turning. 

Aside from a 4WD not disengaging, symptoms of a seized differential include a loud grinding or clunking noise and the smell of burning oil.

4. Low Lubricant

To keep the four-wheel drive system running smoothly, it needs a steady lubrication supply. Depending on the make and model of your truck, this could either be a type of gear lubricant or transmission fluid. The lubricant prevents each gear and bearing from overheating and seizing. 

If the fluid level drops too low, begins breaking down, or contains contaminants, it may be unable to lubricate the differential gears properly. You may also feel your steering wheel shake in this case. 

If your 4WD system won’t disengage and you notice an oil puddle under the differential or transfer case, that’s likely why the 4-wheel drive won’t disengage.

5. Defective Transfer Case Control Module (TCCM) or Shift Motor

The TCCM is a complex electronic device that monitors the vehicle’s speed, wheel speed, and other factors to determine when and how to shift the transfer case in and out of the four-wheel drive. 

The shift motor receives signals from the TCCM to engage and disengage the shift forks. If the shift motor or TCCM has a faulty electrical connection, it can prevent the 4WD system from disengaging.

Alternatively, it could be a faulty relay.

6. Bad Vacuum Switch or Vacuum Hose 

The vacuum switch controls the flow of vacuum needed to engage and disengage the front axle. The vacuum hose or vacuum lines connect the vacuum switch to the vacuum actuator, which engages the axle. 

A faulty vacuum switch or a leak in the vacuum lines can be enough to prevent a 4WD system from disengaging. 

7. Issues with the Encoder Motor

The encoder motor is responsible for providing feedback on the position of the transfer case. A faulty encoder motor may not be able to provide accurate feedback, causing the 4WD system to remain engaged or engage and disengage intermittently. 

Now that you know why your 4-wheel drive may not disengage, let’s explore some solutions you can try. 

6 Fixes for the 4WD Not Disengaging

Here’s some troubleshooting you could try at home: 

  1. Disconnect the battery: The battery provides power to the transfer case. Removing the battery cuts the power to the transfer case actuator, which can make the gears shift more easily.
  1. Reverse your truck: If you have a manual transmission, ensure your truck is in neutral and activate four-wheel drive high mode. Then, reverse about 100 yards. Running the drivetrain in the opposite direction may release any tension build-up. Alternatively, try driving forward a short distance in 2H mode. 
  1. Press the brake: In older four-wheel drive vehicles, especially those with manual hubs, pressing the brake pedal as you switch from 4WD to 2WD can help free a stuck diff lock.
  1. Check the fluid levels: Check the differential and diff lock have enough oil. Also, remember to change the fluids regularly to prevent contamination.
  1. Look for any leaks: If you notice oil puddles underneath your truck, fix the leak and top up the fluids.
  1. Apply penetrating oil: If you have a stuck drive shaft or manual hubs, apply some penetrating oil before cycling the locking mechanism and moving the steering wheel. 

If you have a damaged switch, jammed manual hubs, or are just out of luck, book a service with a trained mechanic.

No doubt, four-wheel drive is a game changer off-road. 
But what happens if it won’t disengage but you need to drive?
Let’s take a look.

Can You Drive When the 4WD System Doesn’t Disengage?

Driving on regular asphalt with the four-wheel drive engaged is technically possible, but you should avoid it.

Since the system isn’t designed for smooth, dry pavement, driving on such surfaces with the 4WD system on can make the steering wheel feel stiff. It can also damage the tires, drive shaft, differential, shift motor, and axle.

No one wants a stuck 4WD. Let’s check out a few things you can do to extend its lifespan.

4 Tips to Protect Your 4WD System

Here are some preventative maintenance tips to protect your four-wheel drive system: 

  1. Only engage four-wheel drive when necessary: Driving with 4WD on a dry, smooth road can damage your 4WD system, especially in older vehicles. Therefore, you should only use four-wheel drive when necessary, such as on ice, snow, or mud.
  1. Choose the correct four-wheel drive mode: Most four-wheel drive systems have several modes, such as 4H (high range) and 4L (low range). The high range is ideal when stuck in snow, ice, or mud. The low range is for tougher situations, such as climbing or descending steep hills.
  1. Shift into four-wheel drive when the vehicle is at a complete stop: In older 4WD vehicles, engaging and disengaging at a complete stop is essential to avoid damage. 
  1. Drive slowly while four-wheel drive is active: Four-wheel drive doesn’t improve handling on slick or icy roads. If you’re driving faster than conditions allow, you’ll be at an increased risk of flipping your vehicle.

Next, let’s dive into the cost of fixing a damaged four-wheel drive system. 

How Much Does it Cost to Have a 4WD System Repaired?

A general diagnosis of your vehicle is likely to cost between $88 and $111. However, the actual cost of repairs will depend on the part and labor. For example: 

Wrapping Up

A stuck 4WD system is something many off-road enthusiasts have experienced, but it can be a serious roadblock. Although preventative maintenance goes a long way, sometimes the hubs won’t disengage. 

If you’ve tried troubleshooting, avoid driving it on the road and get an expert to sort it out for you.
Like AutoNation Mobile Service!

We’re a mobile auto repair service available seven days a week and offer easy online booking. All our services come with a 12-month | 12,000-mile warranty.

Contact us today and get all your auto repair needs fulfilled right in your driveway.