79 Series Diff Lock: Factory vs Aftermarket - A 2026 Buyer's Guide
Diff locks are one of the most-asked-about 79 Series modifications and one of the most expensive when fitted aftermarket. The factory availability has shifted across the years - early 79s had no factory lockers at all, the V8 GXL era introduced the factory rear locker as standard, and the 2024 facelift GXL now ships with front and rear lockers standard. The aftermarket upgrade decision depends on which variant and model year you have and how seriously you use the truck off-road.
This guide covers the factory options by year and trim, the two main aftermarket lockers, when each makes sense, what they actually cost fitted, and what the trade-offs are. Where factory equipment is quoted, the year-by-year detail matters because the 79 Series has evolved significantly over its three-decade production run. Always cross-check the build plate, compliance plate and original order documentation on any used 79 to confirm what is actually fitted.
1. What a Diff Lock Actually Does
A differential is the gearset that allows the two wheels on an axle to spin at different speeds, which is what lets a vehicle turn corners. An open differential sends torque to whichever wheel has the least traction, which is why an unlocked vehicle on a steep climb with one wheel in the air will spin that airborne wheel and go nowhere. A diff lock physically locks the two wheels on an axle together so they rotate at the same speed regardless of available traction. Both wheels get equal torque and the vehicle climbs.
This matters most in extreme low-traction conditions - climbing rocky steps, crossing diagonal obstacles where one wheel is unloaded, deep mud where wheel slip alternates side to side. On sealed roads, gravel, and most sand, a diff lock is either useless or actively harmful (locked diffs cannot handle cornering properly and stress the drivetrain). The diff lock is an off-road-only tool, used briefly when conditions require it.
2. Factory Diff Locks by Model Year and Trim
The 79 Series factory locker history matters when shopping used. Early 79s (pre-V8 era HZJ79) had no factory lockers - they relied on the part-time 4WD system plus driver skill. From the V8 introduction (2007) the factory rear electric locker became standard on the GXL trim with the front locker as an extra-cost option that some buyers ticked and most did not. Workmate variants in the V8 era typically did not get lockers at all from factory.
From the September 2022 update, factory locker fitment broadened. The 2024 facelift range introduces the new GX trim between Workmate and GXL. On the current model: the GXL ships with both front and rear electric lockers as standard; the Workmate and GX get the same locker hardware as a $1,500 factory option box. Older vehicles need to be confirmed by checking the compliance plate, the build sheet and the dash button layout - the locker buttons are absent on vehicles that left the factory without them.
3. Factory Locker Engagement Behaviour
The factory Toyota locker has known engagement quirks that are worth understanding. Engagement is electric, switched from a dash button, and only operates in low range. The system also has safety parameters that require the vehicle to be essentially stationary and the wheels to be aligned within a small tolerance before the locker will actually engage. In practice this means a few moments of fiddling, sometimes rocking the vehicle, before the locker physically engages and the dash light goes solid.
The behaviour is fine in deliberate technical driving where the driver pauses, engages the locker, then proceeds carefully. It is less ideal in fast-changing off-road conditions where engagement timing matters. This is one of the reasons some serious off-road owners with factory-locked GXLs still fit aftermarket lockers - the engagement responsiveness can be the difference between climbing the obstacle and rolling back into it.
4. ARB Air Locker - The Aftermarket Standard
The ARB Air Locker is the most common aftermarket front locker fitment on the 79 Series. It uses a compressed-air actuator (driven by an under-bonnet compressor) to engage the locker via a clutch and dog-tooth mechanism. ARB has been making these for over 30 years and the reliability record is excellent. Fitted price for a front Air Locker including compressor, switches and wiring is typically $2,500 to $3,500 in 2026.
The Air Locker advantage is responsiveness - engagement is essentially instant when the switch is activated, and it can be disengaged just as fast under load. The disadvantage is the compressor requirement - a typical compressor install adds a few hours of work and around $400 to $600 in compressor cost (although most owners pair the locker with an ARB compressor they were going to fit anyway for tyre inflation). The Air Locker is the right choice for owners who want immediate engagement and who already have or plan to add a compressor system.
5. Eaton e-Locker - The Electric Alternative
The Eaton e-Locker is an electrically actuated locker that competes directly with the ARB Air Locker. The actuation is via a small electric motor that engages the locker mechanism, with no compressor or air lines required. Installation is simpler than the ARB because there is no air plumbing. Fitted price for a front e-Locker is typically $2,000 to $3,000 in 2026, slightly cheaper than the ARB once compressor cost is factored in.
The e-Locker advantage is install simplicity and no compressor dependency. The disadvantage is engagement responsiveness - the electric actuator is slightly slower than the air actuator, particularly under load when the locker is being asked to engage with the axle already turning. For most off-road use cases the difference is irrelevant, but for technical rock crawling where engagement timing matters, the Air Locker is preferred. For touring and general off-road use the e-Locker is the right call.
6. Traction Control vs Diff Lock
The 79 Series has factory traction control (Active Traction Control or A-TRC depending on year) that brakes individual wheels to redirect torque to the wheel with traction. In effect, A-TRC mimics what a diff lock does, by applying brake force to a spinning wheel rather than locking the axles together. On gravel, sand and moderate off-road conditions, A-TRC is genuinely effective and a fully unlocked 79 can do more than most owners expect. A-TRC has been factory-fitted across most variants since around 2012, though pre-A-TRC vehicles rely on driver skill and physical lockers only.
Where A-TRC runs out is in extreme conditions where the brake-based traction redirection cannot apply enough force fast enough, or where brake heat builds up across repeated cycles. Steep loose climbs, deep mud, technical rock work all eventually defeat A-TRC. At that point a mechanical diff lock is the only thing that gets the truck up the obstacle. A-TRC is good enough for the touring use case; diff locks are required for the serious off-road use case.
7. Install Process and Workshop Time
Fitting an aftermarket locker is not a DIY job for most owners. The differential needs to be disassembled, the locker mechanism installed, the gear backlash and pinion preload reset to factory specification, and the diff carrier cap torqued. A workshop with diff specialist tools is required for proper setup, and incorrect setup will destroy the diff within a few thousand kilometres. Plan on a full day in the workshop ($600 to $1,200 in labour on top of the locker price).
If you are doing the locker install at the same time as other suspension or driveline work (CV upgrade, lift kit, axle service), the combined labour is more efficient because the workshop has the truck on the hoist anyway. Bundle the locker install with a planned suspension upgrade and save 20 to 30 per cent on combined labour. Most reputable 4WD workshops in Australia have ARB and Eaton certification and competitive quotes.
8. When Aftermarket Lockers Matter and When They Do Not
Aftermarket lockers matter when (a) you have a Workmate, GX or older variant without factory lockers and you drive technical off-road terrain, (b) you have a GXL but find the factory locker engagement too slow for your driving style, (c) you tour solo or in remote areas where being stuck is a serious problem, or (d) you compete in 4WD events. In those use cases the locker is the difference between climbing the obstacle and winching out backwards.
Aftermarket lockers do not materially matter when (a) you have a current GXL with factory lockers and your driving stays within their engagement envelope, (b) your driving is mostly sealed road and gravel touring, (c) you stick to formed 4WD tracks rated for any 4WD vehicle, or (d) you travel in groups where the others can pull you out if you do get stuck. In those use cases the factory setup plus A-TRC is sufficient and the locker money is better spent on suspension, tyres, recovery gear or fuel range.
9. Total Cost of Ownership
Ticking the factory diff lock option at order stage on a new Workmate or GX adds $1,500 to the new vehicle price and delivers both front and rear lockers - the cheapest path to a fully locked 79 by some margin. Retrofitting an aftermarket ARB Air Locker on a single axle costs $2,500 to $3,500 fitted plus another $400 to $600 if a compressor system is needed. Retrofitting an Eaton e-Locker on a single axle costs $2,000 to $3,000 fitted with no compressor dependency. Maintenance is minimal on either aftermarket option - both have factory-style reliability.
Resale impact is real but modest. A used 79 Workmate or GX with the factory diff lock option fitted commands $2,000 to $3,500 more than an equivalent vehicle without. An aftermarket ARB Air Locker adds around $1,000 to $2,000 to resale value (less than the original install cost). Most owners who fit an aftermarket locker do so because they need it, not as an investment - but the resale offset means the net cost over a 5-year ownership cycle is genuinely affordable.
Frequently Asked Questions
Does the 79 Series come with a diff lock from factory?
It depends on the model year and trim. On the current 2024 facelift, the GXL ships with both front and rear electric diff locks as standard. The Workmate and GX get them as a $1,500 factory option at order. V8-era GXLs (2007 to 2023) typically had the rear locker standard with the front as an option that may or may not have been ticked. Pre-V8 vehicles generally have no factory lockers. Always check the build plate and dash button layout on used examples.
How much is the factory diff lock option on a new Workmate or GX?
The factory diff lock package on a new 79 Workmate or GX adds $1,500 to the order price and delivers both front and rear electric lockers. This is the cheapest path to a fully locked 79 - much cheaper than retrofitting either ARB Air or Eaton e-Lockers later.
Should I fit an aftermarket diff lock on my 79 Series?
If you have a Workmate, GX or older variant without factory lockers and you regularly drive technical off-road terrain, yes. If you have a current GXL with factory front and rear lockers, the aftermarket case is weaker - some owners still fit them for engagement responsiveness in technical driving. If your driving is mostly sealed road and gravel touring, no - the factory setup plus A-TRC is sufficient.
How much does an ARB Air Locker cost fitted in 2026?
A front ARB Air Locker on a 79 Series typically costs $2,500 to $3,500 fitted including installation labour. Add $400 to $600 if a compressor system is required (most owners are already fitting one for tyre inflation, so the marginal cost is small).
ARB Air Locker vs Eaton e-Locker - which is better?
The ARB is more responsive on engagement under load and is the standard choice for technical rock work. The Eaton is simpler to install (no compressor required) and slightly cheaper fitted. For touring and general off-road use, the e-Locker is the right choice. For competition rock crawling, the Air Locker is preferred.
Will a diff lock damage the 79 Series drivetrain?
Not when used correctly. Diff locks must be disengaged before turning on sealed surfaces or hard gravel, because the locked axle physically cannot allow the two wheels to rotate at different speeds. Used as intended - in low range, on loose or slippery surfaces, briefly - they have no negative effect on the drivetrain.
