Harrop Engineering

Like most Aussies I knew the Harrop name since childhood because of Ron Harrop’s drag racing FJ Holden and he and his dad’s long association as the engineering muscle and innovation behind racing greats like Norm Beechey and Bob Jane. Later it was the Holden Dealer Team and once again, Harrop innovation ruled the tracks.

Those might have been sealed race tracks instead of the dirt tracks we four wheel drivers love but the fact is Harrop’s association with the American Eaton Corporation led to the development of the greatest innovation in Aussie four wheel driving since the original air locker design was taken in-house by ARB back in the 1970’s.

Yep, the fact is that until you ‘lock’ the differential in a four wheel drive axle, you’re not really driving both wheels. There’s been some limited slip diffs that work reasonably well – it hurts me to say this but Nissan’s was the best – but nothing beats the total security of a locked axle. Most importantly given the weird conditions some of us put our vehicles into, you have to be able to lock and unlock both axles at will.

Air Lockers did the job well and Pro Lockers came out offering similar technology. I used both for over twenty years, more than long enough to discover their limitations were always in the air systems required to push the internal locking piston. Because they require constant pressure you have to have a compressor, air lines, fittings and the O rings that hold that pressure all functioning perfectly at all times. Even so, they worked remarkably well.


And then along came Harrop with their development of the Eaton ELocker featuring an electromagnetic locking mechanism that solves all the issues of running compressed air into your diffs. I trialed a couple in Milo and straight away found they meshed perfectly at the touch of a button, and most importantly to us dedicated users, instantly un-meshed when you pushed the button too! A couple of wires replaced all the complexity of air plumbing and her presto, welcome to the new age of locking differentials!

If you’ve ever seen the Harrop manufacturing plant in Melbourne then you’d know why I’m impressed by their engineering standards. How impressed? Harrop’s ELockers are already up both ends of Milo 2. You can do a lot of things to make a standard four wheel work better off road but ELockers are absolutely top of the list!

Watch the video below to see what the boys and I had to say about the Harrop E-Lockers when we used the during the Roothy’s LowRange series.