How Do Locking Hubs Work?by Hannah Scott
There are many facets to a working 4x4 vehicle. From having good sized tires, a powerful motor to having enough gas, your 4x4 has a lot to do to keep you moving through that mud in the 40 acres of your backyard or up that steep, rocky hill that you and your friends have been trying to get to the top of for years. But, none of that 4x4 power will work efficiently or at all without locking hubs. That is where it all begins. What are locking hubs and how do they work?
Locking hubs are located at the front of your 4-wheel-drive vehicle. They may look like innocent little dials in the middle of your two front wheels, but there is slightly more to them. The hubs are, essentially, an axle split in half (right and left). They work separately, spinning free of each other and allowing the drive from the rear axle to push them wherever you steer them. This is two-wheel-drive mode, just like a rear-wheel-drive car. When they are unlocked, you do not have the ability to put your vehicle into 4WD.
Newer 4x4 vehicles are manufactured with automatic locking hubs. This enables you to be able to "shift on the fly" into 4WD. The process to this is complex, yet simple in explanation. When the shift lever is moved into position, the changing gear creates an inertia that "locks in" the hubs.
When you "lock in" your hubs, you are connecting the two half axles to a drive plate that locks them together, making them turn as one unit. They will spin freely together, ready for you to engage the 4x4 which will send drive power to them via a differential from the transfer case.
Modern vehicles have automatic locking hubs that require little to no manual operation from the user. However, some of these newer vehicles still allow for manual operation as a backup in case the automatic locking hubs fail.
Older 4WD vehicles had manual locking hubs and were referred to as "part-time" 4x4 because the half axles moved freely of each other like a 2WD car. On these models you had to exit your vehicle to turn a dial on the hub of each front wheel from "free" to "lock" and then get back in and set your transmission into the "neutral" position before engaging 4x4. It is not uncommon to "lock in" the hubs during winter snowfall and drive around until you need to put the vehicle into 4x4 mode.
Some models were made as "full-time" 4x4. On these models the front axle turned freely as one unit until the 4x4 was engaged, but you still had to put your vehicle into the "neutral" position to engage 4x4.
There are manufacturers like Warn (www.warn.com) that make manual locking hub replacement kits for automatic locking hubs. Manual locking hubs are sought for off-road enthusiasts. The manual nature of locking the hubs provides controlled operation of the vehicles in different terrain.
Hannah Scott has been a freelance writer for more than 12 years. Scott's first published article appeared in "The Mountain Press" in 1999. She has also written for the "Tennessee Star Journal" and several websites, including RAE Magazine.