Posted on: 27 June 2017Share
As automobile manufacturers become more sophisticated and try to roll out vehicles that appeal to a demanding marketplace, so certain components become more complex. This is increasingly the case when it comes to the type of differential fitted to the modern-day vehicle. In particular, sport utility vehicles and four-wheel-drive trucks now often come equipped with locking hubs. What are these, and what should you do if you suspect a problem?
What Do They Do?
The objective of the automatic locking hub is to uncouple the front wheels from the system whenever four-wheel drive is not needed. This will of course reduce the amount of wear and tear on that particular axle and will frequently give the driver better economy. Nevertheless, when a driver wants to engage in some off-road driving, they will require the automatic hubs to work correctly, and sometimes they don't.
What Happens When They Fail
One of the main reasons for failure is a buildup of dirt, mud or even corrosion within the locking mechanism that causes it to simply fail to engage. One of the first signs of this will be some odd grinding noises when the vehicle is shifted into four-wheel-drive. You might not be sure where the noises are coming from and might initially think it's to do with the transfer case. However, often it is the locking hub.
Conversely, you might not be able to disengage the hub, and if this is the case, you may notice a rhythmic "drumming" noise from underneath when you are driving on paved roads. You'll also find that the overworked drivetrain is starting to wear your front tyres down too quickly, and you'll certainly notice increased consumption at the fuel pump.
Testing at Home
You can check what's going on by putting your transmission into the "park" position and lifting one side of the vehicle off the ground with a jack. When it is in two-wheel drive mode, you should be in a position to turn the free wheel quite easily. If it is more difficult to turn and you notice that the axle shaft is also turning, you will know that the hub is still engaged.
To test further, rotate the stationary axle shaft backwards slowly to see if it locks the hub as it should. Then try turning the wheel again and see if it and the shaft move in tandem.
As a final test, grab the axle shaft with one hand and move the road wheel in a reverse direction with your other. This ought to disengage the mechanism, and you should then be able to turn the road wheel freely again.
Getting the Fix
If the vehicle fails any one of these tests and the hub is not unlocking or locking correctly, then the mechanism will need to be taken apart to see what is happening. For this you have to contact a differential repair specialist at a company like Precision Automatic Transmissions to get to the bottom of it.