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.