Harrop ELocker

The Eaton/Harrop ELocker is a simple, effective and affordable locking diff for your 4x4. We check out the Harrop factory and test the ELocker.

Why use a locker?

Ask anyone who has ever driven off road, on ice or up a slippery boat ramp and they will tell you that without some sort of traction aid, driving on such surfaces is near impossible and can be dangerous. By traction aid, we’re referring to electronic traction control (ETC), a limited slip differential (LSD) or a locked or locking differential. By far the most effective of these is a locking differential on both the front and rear axles.

Without some sort of traction aid, as soon as one wheel loses grip, the very action of the unlocked or open differential will send all the drive to that spinning wheel while its partner at the other end of the axle does nothing. With the differential locked, the drive has no choice but to go to both wheels and hopefully the one on the opposite side from the spinning wheel will have enough grip (traction) to propel the vehicle. In a 4x4 vehicle, that applies to both the front and rear axles separately. They each have a differential in between the two wheels and ideally you want to be able to lock them both so that all four wheels and tyres are getting drive from the power train.

Why choose a selectable locker?

When you drive your car on the road, you need differentials. The diff allows the wheels on an axle to spin at different speeds. As you turn corners the outside tyre travels further and hence at a faster rate. But when you’re in a low traction situation like those described above, you want to be able to lock the differential and hence the wheels so they both get drive. Simply by pushing a button or flicking a switch to activate the diff lock, you can get over or through an obstacle.
You also want to be able to unlock your diffs so you can turn and manoeuvre the vehicle. Even on a loose or slippery surface, locked diffs, particularly on the front axle, will make it harder to turn and increase your turning radius. Being able to lock and unlock diffs as required allows you to manage this situation.

Why choose an ELocker?

The Harrop/Eaton ELocker is a strong unit. They are made aftermarket to accommodate more than the regular loads put on standard vehicles. Oversize tyres and more power and torque will exert an increased load on drivetrain components. On a torque test rig, 10,025Nm of torque was put in to a Harrop ELocker before the axle broke, not the ELocker differential.

Other locking diffs are tough too but an advantage of the ELocker is its simplicity. Many other lockers are air activated and require an air compressor and associated lines and hardware to operate them. While it’s always handy to have a compressor mounted in your vehicle, the Harrop ELocker doesn’t need one. It just uses simple power wires running to it via a switch for operation. This theoretically makes the ELocker easier and cheaper to install with less to go wrong with it.

When the ELocker is activated by the driver, current flows to an electromagnet within the diff. Friction then forces the locking pins in to the side gears to lock the opposing axles. Simple and effective.

Harrop Engineering

Melbourne’s Harrop Engineering has taken a product from the USA and tailored it to suit an Australian 4x4 market that has a strong appetite for new and innovative equipment.

Differential locks have been around in varied forms for decades, as have electronically activated diff locks which are the chosen type for most original equipment manufacturers (OEMs). Companies like Ford, Chevrolet, Jeep, Nissan, Mitsubishi and Volkswagen, all currently equip their 4x4 models with manually selectable, electronically activated diff locks. Several OEMs source their locking digs from the driveline manufacturing giant Eaton.

Eaton, which manufactures the popular Detroit and TruTrac lockers and Posi limited slip differentials, first developed its ELocker to fit in the HMMWV (Humvee) military vehicle from AM General and soon adapted the product for civilian applications in other 4x4 vehicles.

However, this product was mainly used in US-centric vehicles such as full-sized pick-ups and Jeeps, and as Australia’s taste in 4x4s differs from the US, the usefulness of Eaton’s ELocker in this country was limited.

That’s where the folks at Harrop stepped in. The familiar Harrop name is best known in Australia for its motor racing and high performance products due to the exploits of company founder Ron Harrop.

Harrop Engineering is now a major manufacturer of high performance parts such as brake components, intake systems and superchargers and also OE components in its aluminium foundry and machine shop. Via its supercharger development with Eaton in the USA, Harrop zoomed in on the locking differential product and saw the potential for the ELocker in Australia.

The limiting factor for the Eaton ELocker in Australia was its product range. Toyota Land Cruisers, Prados and Hiluxes, Nissan Patrols, Navaras and Land Rovers, which are among the top selling vehicles in Australia, were simply not on the radar for Eaton in the USA. But with Harrop’s local manufacturing and engineering skills, these limitations could be overcome.

Harrop Engineering now has the steel carriers for the ELocker cast locally in Australia and then machined in-house at its Preston, Victoria facility to suit the country’s popular 4x4 applications. They are totally machined so that there are no casting marks left on the product, and as with other components manufactured at Harrop Engineering, they are checked for accuracy on the Co-ordinate Measuring Machine (CMM).

The diffs are hand assembled at Harrop using a combination of parts manufactured locally and sourced from Eaton in the USA.

The locking mechanism is still Eaton’s while many other parts have been optimised for our 4x4 applications. The four-pinion design of the current ELocker came as part of Harrop’s input to improve the strength of the Eaton unit

Each ELocker is tested for operation, then has a protective coating applied to it and is finally packaged in a tough-case style plastic box for shipping out to Harrop’s distributors around Australia and world wide.

The range of Harrop ELockers covers around 90 per cent of the popular 4x4 models currently available in Australia – 34 part numbers are currently in use with more to come. Harrop also exports the ELocker back to the USA and to many other countries.

ELockers are available direct from Harrop headquarters in Melbourne and the workshop there can ‘factory fit’ the diff to your vehicle if you want it done by the manufacturer.

Alternatively, both Opposite Lock and Terrain Tamer distribute the Harrop ELocker through their stores nationally. Many of those stores can also do the installation in your vehicle.

On track

After seeing how the Harrop ELocker is made and operates, 4X4 Australia wanted to see how it works in a 4x4 vehicle, so we grabbed Harrop’s own dual ELocker equipped 120 Series Prado and headed out to Terrain Tamer’s purpose-built, offroad test track.

The newly created test track had trouble stopping the Prado with its factory electronic traction control and long-travel rear suspension, so it took some creative lines though the course and a bit of digging for us to pick up some wheels.
Unlike most factory fitted locking diffs, the ELocker can be activated at any time when the vehicle is stationary. That doesn’t mean you should drive around with the lockers activated, but you can operate them in both high and low range.

The actuation is fairly instantaneous from the time you flick the switch but you do need to be stationary to have the gears lock in. You can lock either the front or the rear axle, independent of each other or together for ultimate traction. We had the Prado spinning its wheels on a steep climb with the ETC working overtime but getting nowhere. After stopping and holding the vehicle on the foot brake, we switched in the rear locker and the Prado was able to drive over the hill.

Coming back to the ruts we dug in the track the first time, we put the Prado into a position where all four wheels scrabbled for grip – even with the rear diff lock in. No problem. We simply stopped, switched in the front lock and away we went. The Elocker is just as easily unlocked as well.

Using ELockers requires correct track assessment and appropriate use of the tools to do the job correctly.

Don’t get stuck and then use the tools – in this case, the lockers – to get you out of trouble. If the track ahead looks challenging use a variety of means – correct tyre pressure, low range, lockers, even the kitchen sink if you think it will get you through.

If there is a steep turn at the top of a difficult climb, you need to be ready to unlock the front diff so you can safely make the turn. It’s all assessment and knowing how to use the aids you have at your disposal.

We say: Strong, simple and dependable.
Price: RRP $1499
Contact: www.harrop.com.au

Get the latest info on all things 4X4 Australia by signing up to our newsletter.