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TJM Pro Locker: 4x4 product test

By Mark Allen, 26 May 2019 Gear

TJM Pro Locker review feature

TJM Pro Lockers transform the Tonner into a tough tourer.

LONG suspension and long-travel sway bars make a huge difference off-road by allowing all wheels to keep a firm grip on the ground; the more grip, the more drive you maintain and the farther up the track you get. But that off-road-honed suspension is probably going to be terrible on-road.

That’s where cross-axle diff locks come into play; while they’re great off-road for those who like to push the limits, they also allow tourers the safety and increased ability to easily and safely tackle any obstacle. They also limit track damage thanks to less or no wheelspin.

I’m no stranger to TJM Pro Lockers, having had zero problems in the eight years they were in my 105 Series Cruiser. In the process of setting up my One Tonner I figured I’d stick with one of the rear diff-mounted, air-operated Pro Lockers. Using GQ Patrol diff centres allowed for easy purchase and fitment; although, there is a good selection of vehicles that can have Pro Lockers fitted as standard.

Follow the Custom Holden One Tonner build

How the TJM Pro Locker works

THE TJM Pro Lockers are an air-operated locker that forces air into the diff from an onboard air compressor via an airline, which engages a locking ring over one axle gear. This in turn locks the carrier and pinion gears, forcing drive to be sent to both left and right wheels equally. There is no chance of an axle-set losing drive to one wheel or another midway through any obstacle.

Once you’re through the obstacle a flick of the switch will return the diffs back to standard open units by allowing the pressurised air to be released through an exhaust port in the solenoid valve. The locking ring that joins the axle pairs together via the internal gears is released via an actuator, which allows your diffs to differentiate and then its drive-time as normal.

Having had Pro Lockers fitted to my old Cruiser and now the mighty Tonner I can’t imagine being without them – they’ve been that good. There have been plenty of times when perhaps they weren’t needed, but I’ve used them anyway as insurance to help through tough spots.

The Pro Locker’s ability to be switched ‘on’ or ‘off’ at the flick of a switch with no chance of unlocking when needed most, whether you’re in forward or reverse gear, is a positive. Once the initial air compressor switch is activated and the airlines are allowed to build up pressure, the diff lock activation is near-on instant.

Of course, there are airlines to run under the body of the Tonner, which, when fitted correctly, won’t snag. Plus the entry point into the diff is afforded extra protection with a second layer of tubing and a solid brass fitting tapped into the top of the diff.

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Does the TJM Pro Locker have downsides?

THE front and rear Pro Lockers fitted to my Cruiser were brilliant in their operation, but steering was extremely difficult when the front was activated. While not a design fault – and losing steering with any front manual locker is to be expected – there were times when it would be beneficial not to turn the front locker on. That’s why I’ve opted to go for a rear-only Pro Locker in the Tonner, as it’s more useable more often.

The only gripe with the system is with the compressor. The current standard offering is tiny compared to the larger, more versatile unit in my Cruiser. It does a stellar job of activating the locker when needed, but it can’t be used for tyre inflation or any other associated task.

This means you need to carry a second air compressor or swap the supplied TJM Pro Locker compressor with a larger unit. Not that I’ve done it yet, but the second option of fitting an onboard, high-flow compressor is what I’ll be doing.

What are the advantages of the TJM Pro Locker?

WHEN used correctly that rear locker, or a pair of front and rear lockers, will be the most advantageous piece of aftermarket equipment to help your 4x4 go further. Provided you drive correctly you’ll be able to negotiate more severe tracks without damage to either your vehicle or the track. Even though the locked 4x4 may still lift its wheels off the ground, the constant and equal drive will more often than not keep the vehicle headed the way the driver intended. 

While the Pro Locker is said to be strong enough to handle the comp-bred driver with oversized rubber, it is equally at home in any touring 4x4. Being able to slowly negotiate obstacles without damaging your pride and joy is a huge plus, as is not damaging the track itself via wheelspin.

Driving a wrong line or pushing the rules of gravity may see your 4x4 land on its lid, so caution must still be exercised when driving with lockers; you might have traction, but your 4x4 will keep on crawling almost regardless of the grade’s steepness.

There are other uses for a rear-fitted locker: during steep descents the locked rear axles won’t allow overrun and will stop one side speeding up; you’ll get improved grip during downhill engine braking; it can be used on slippery boat-ramp exits; and it can be used to help reverse a heavy caravan up a hill. It can realistically be used at any time, even in 2WD; just remember not to allow axle windup on solid or high-grip surfaces.

I’ll wager that once you have been locked there’s no going back to an open diff centre.

Prep yourself with 4x4 gear

Available from: www.tjm.com.au
RRP: $1577 (rear GQ Patrol Pro Locker); $220 (Pro Locker compressor)
We Say: Zero problems from years of use