How to Check If Your Transmission's Hub is Locked in Place

If you think that you have an emerging problem with your vehicle's differential, it could be that your locking hubs are playing up. Locking what, you may ask? These days, a lot of manufacturers are fitting this type of system as standard equipment on four-wheel-drive trucks and SUVs, but what are they for and what could be going wrong?

The Need for the Locking Hub

The automatic locking hub allows your vehicle's computer to disconnect the front wheels from the transmission system when they are not needed for additional traction. On the other hand, if you are in off-road situations and need all the help you can get, the hub can be locked into place instead. For everyday driving, broadly speaking, a disconnected hub system can give you better fuel economy and reduce the amount of wear and tear on your vehicle.

Locking hubs are, like many other components on your vehicle, subject to issues. For example, dirt, mud or even corrosion could build up and prevent the system from engaging or disengaging. One of the first signs of trouble will be an unusual grinding noise whenever you try and move the vehicle into 4WD. You may be tempted to think that the central transfer case is at fault, but more often than not it will be the locking mechanism.

Likely Issue

If you find that you've been able to engage the hub but that it will not switch off and have also noticed a "drumming" noise when you're driving along the open road, this could indicate that the transmission is locked "on" when it doesn't need to be. In the long term, you will notice additional wear on the front tyres, as well as poor fuel economy.

How to Diagnose the Problem

If you're not sure whether this is the problem, a series of simple checks should help you. Elevate the front of the vehicle on the driver's side with a jack, while the transmission is in the park position. You ought to be able to turn that front wheel quite easily by hand, if the system is in two wheel drive mode as it should be. However, if the axle turns at the same time it means that the hub is locked "on."

You can perform another check by turning the axle shaft itself towards the rear and this will engage and lock the hub. When you try turning the wheel forward with your hand next, the shaft should turn at the same time.

Then, grab hold of the axle shaft with one hand and turn the wheel backwards with your other. Usually, this will disengage the mechanism and you should hear a distinct "click" as it does so. Once again, you should be able to rotate the driving wheel by hand quite easily.

Looking Further

These tests should enable you to check if the hub is locking and unlocking as it should. If any one of the tests fails, you should take the vehicle into a differential specialist to find out what's going wrong. For more information about automotive repairs, contact a professional.