If you hear a grinding noise when engaging the 4×4 or the 4WD is not engaging or working intermittently, there could be a few different problems with the vehicle. Find out how to fix this problem with a truck that has 4×4 and auto-lock hubs grinding and working intermittently.
What Can Make 4WD Work Intermittently or Cause Grinding Noises?
If you hear a grinding noise when engaging the 4×4, also known as four-wheel drive (4WD), or it’s not working and you have auto-lock hubs, it’s because the hub is not able to move in and out. It connects to outside of the CV shaft and has a nut, which is known for loosening even after being torqued properly.
The growl or grinding noise will indicate which wheel has the problem, and it’ll sound like two gears running together but not aligning, which means the shaft is not engaged.
To diagnose the 4WD that has trouble engaging and is working intermittently, you’ll want someone inside the truck so they can put it into 4WD. Then you can make sure the 4WD motor is working at the transfercase and check for vacuum and make sure the actuator is clicking in and out.
How to Fix a 4×4 Making a Grinding Noise and Not Engaging or Engaging Intermittently
You’ll need an assistant to engage the 4WD so it can be inspected.
Steps to fix a 4×4 engaging intermittently and making a grinding noise
- Raise the Truck Up on Jack and Jack Stands
Raise the truck up with a jack and jack stands to get underneath. You want to have your safety in mind and do what you know is safe. Make sure the jack stands are sturdy, because you’ll have an assistant starting the vehicle and putting it in 4WD so the wheels can spin.
- Start the Vehicle and Engage 4WD
Have an assistant start the truck and engage the 4×4 to see how well the 4WD system works.
- Find the Vacuum Actuator and See If the Wheel Spins
Find the vacuum actuator at the back of the auto-locking hub. It has a vacuum line placed down into it. Have the assistant put the truck into 4WD High, let go of the brakes, and let the wheel spin. If you can see the wheel spin, you’ll know its working. This tells you have vacuum down at that area, the electricals are working, and the motor in the transfercase is working.
- Lower the Vehicle
After assessing the 4WD, lower the vehicle to check the hub actuator nut on the wheel that has the grinding noise.
- Take the Wheel off
Loosen the lug nuts with the truck on the ground, raise the wheel with the grinding noise, remove the lug nuts, and remove the tire.
- Check Vacuum Hub Actuator Nut for Looseness or Damage
Remove the cap from the wheel hub axle nut with a pick. Press the nut in. It should not move and there should be no play or looseness.
Remove the hub nut and check for damage to the nut and CV axle splines. If the nut and CV axle are in good condition, re-torque the hub nut.
- Add Thread Locker and Re-Torque the Nut
Look up the torque spec for the nut. Clean the hub actuator nut and axle shaft with parts cleaner. Then add thread locker to the splines, tighten the bolt, and re-torque it. Make sure it’s centered and the axle feels like it’s in the threads. You might need to use a pry bar to secure the wheel and then torque the hub.
In our example we use a 13 mm socket and torque the nut to 20 foot-pounds.
Then check the wheel hub axle nut cap for damage or holes. The cap will prevent moisture or water from getting to the bolt and causing more problems. Tap the cap on lightly with a wrench
How-to Videos: Do More Than Fix a Grinding Noise When Engaging the 4×4
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