WHAT’S THE DIFF?

DIFFERENTIAL LOCKS BUYERS’ GUIDE

WORDS TRISTAN TANCREDI

WANT TO CLIMB INSURMOUNTABLE? YOU’RE GONNA NEED A SET OF LOCKERS.

IF YOU have a penchant for perilous tracks that most of the population steers well clear of, then you’ll need to guarantee drive is delivered effectively to all four wheels. The only way to ensure this is with a pair of front and rear locking differentials.

When driving off-road, a differential will always send power to the wheel with least resistance; so if a 4x4 loses traction (in the air, stuck in mud, etc.) the wheel with the least traction will spin ineffectively. Locking the diffs prevents this by sending equal drive to both wheels on an axis, regardless of terrain or traction, so with front and rear diff lockers (either selectable or automatic) you’ll be able to crawl through most obstacles with little or no wheelspin.

“Lockers are a great investment, as they dramatically improve the vehicle’s capabilities by giving the owner the ability to lock or unlock the differentials as necessary and capture 100 per cent of the available torque and distribute it equally to both ends of the axle,” Harrop’s design engineer, Sebastian Civitarese, told us. “This enables the driver to keep momentum when off-road and safely navigate harsh terrain without losing traction. It’s equally beneficial for the average tourer or when towing on slippery surfaces like boat ramps.

“Ultimately, lockers mitigate the loss of traction,” he said.

LOCKED UP

A COMMON misconception by many 4WD pundits is that by shifting a vehicle into ‘4WD’, power will be sent to all four wheels at all times. However, in certain scenarios a standard vehicle with open differentials will only deliver drive to the easiest wheel to spin on any given axle, which will be the one in a mud hole or up in the air.

“A locker allows you to have full power to both wheels, even when one is off the ground,” said Terrain Tamer parts interpreter, Charlie Dunbar. “So when that wheel lands, you have movement already, allowing you to gain traction and get out of a bad spot.”

ARB’s brand marketing manager, Mark Berger, added: “With a differential locker, you can lock the differential to stop it from spinning the left and right wheel of an axle independently of each other, forcing both wheels to spin at the same rate irrespective of which wheel has traction and which one doesn’t.”

Installing a set of diff lockers and being able to lock and unlock the diffs when required increases a vehicle’s offroad abilities exponentially, with 100 per cent of the available torque able to be equally distributed to both ends of an axle.

As Justin Hettrick, TJM’s suspension and drivetrain product manager, explained, a diff locker provides instant traction: “The off-road ability of almost any 4x4 vehicle is doubled. A locker can be the device that makes you traverse terrain you never thought you would be able to.”

CENTRE DIFF

A CENTRE differential, as the name implies, is positioned - in all-wheel drive and constant 4WD models, like the popular LandCruiser 200 Series wagon - between the front and rear differential. Unlike front and rear differentials, though, a centre diff will split power 50/50 front to rear instead of side to side of each axle. A centre diff lock is essential to ensure drive to both the front and rear axles; although, diff locks front and rear are still required to spread drive evenly from side to side. “Vehicles with a centre diff (and no lockers) can deliver drive to any of the four wheels of the vehicle, but the power will still only be delivered to one wheel and it will still be the wheel with the least traction,” explained Berger.