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Australians Are Back on the Road
Touring is back on the agenda for many Australians this summer. Campsites are booking out earlier, and the highways leading to Victoria’s alpine regions, South Australia’s coast and the Northern Territory’s national parks are expected to stay busy. For 4WD owners, that means making sure their vehicles can cope with heat, distance and load before they leave.
At GJ Drivelines in Keysborough, pre-trip driveline inspections are becoming a standard part of summer preparation. While tyre pressure and fluids are easy to check at home, the differential—the gearbox that divides power between the wheels—often goes unnoticed until it makes itself heard.
What the Differential Does
Every 4WD relies on at least two differentials, sometimes three. Their role is to balance torque between the wheels while letting them turn at different speeds. Without them, tyres would scrub and gears would bind on every corner.
| Differential | Purpose |
| Front | Powers the front axle in 4WD mode |
| Rear | Transfers torque to rear wheels for traction |
| Centre | Splits drive between front and rear axles |
Off-road use, heavy towing and long highway runs all place extra stress on these components. When oil breaks down or seals start leaking, the result is noise, vibration and in severe cases total loss of drive.
Early Warning Signs of Diff Trouble
Owners often mistake differential wear for tyre or suspension noise. Common indicators include:
Whining or humming under acceleration or deceleration
Clunks when shifting between drive and reverse
Oil seepage around the pinion or axle seals
Vibration through the floor under load
Metal flakes in the drained gear oil
If any of these appear, it’s time for a specialist inspection. Differentials can fail gradually, but once the gearset is damaged, a rebuild is the only permanent fix.
What’s Involved in a Differential Rebuild
A rebuild restores the diff’s original clearances and quiet operation.
It’s a precision job that requires experience and measurement tools.
It’s a precision job that requires experience and measurement tools.
Typical workshop process:
- 1. Strip and clean the housing
- 2. Inspect crown wheel, pinion and bearings
- 3. Replace worn bearings, seals and shims
- 4. Set backlash and preload to specification
- 5. Reassemble, torque-check and fill with correct oil
- 6. Bench-test before road testing
At GJ Drivelines, each rebuild is carried out using calibrated equipment and OEM-grade parts, followed by on-car testing to confirm smooth operation.
How the Elements Affect Differential Life
| Condition | Effect | Prevention |
| Dusty tracks | Blocks breathers, introduces grit | Fit extended breathers and check filters |
| Water crossings | Draws moisture into hot housings | Let diff cool before submersion |
| Heavy towing | Raises temperature and bearing load | Use correct oil grade and service regularly |
Even light contamination in diff oil can shorten component life.
That’s why workshops often recommend replacing oil after any deep crossing or extended towing trip.
That’s why workshops often recommend replacing oil after any deep crossing or extended towing trip.
Checklist: Before You Head Out
A short inspection before your trip can avoid major driveline repairs later.
| Check | What to Look For |
| Diff oil level and colour | Should be clean and full |
| Breather hoses | Not blocked or kinked |
| Seals | Dry and intact |
| Tailshaft joints | No play or grease leakage |
| 4WD engagement | Smooth without clunk |
| Unusual noises | Listen during acceleration and coasting |
Any irregularities should be checked by a specialist before you leave Melbourne.
Why Specialist Workshops Matter
Differentials require fine adjustment measured in hundredths of a millimetre.
A rebuild done without proper setup can destroy a new gearset in minutes.
That’s why owners of touring rigs and tow vehicles often choose dedicated driveline workshops instead of general repairers.
At GJ Drivelines, technicians rebuild and balance drivelines for all major 4WDs—LandCruiser, Ranger, Hilux, Patrol and more—using in-house test equipment. The same facility also handles tailshaft balancing, centre bearing replacement and custom driveline modifications.
Simple Habits to Extend Differential Life
- Replace oil every 40,000–50,000 km, or sooner after water exposure
- Keep tyre sizes matched to avoid strain between axles
- Check breathers after each off-road trip
- Let the diff cool before deep crossings
- Avoid heavy throttle when traction suddenly returns on dirt or sand
These habits cost little but make a big difference over time.
Where to Get Help
GJ Drivelines
Keysborough, Victoria
Custom differential rebuilds, tailshaft balancing and driveline upgrades.
4WD Driveline Repairs | Custom Tailshaft Balancing | Parts Store
Frequently Asked Questions
The most common signs include whining or humming under acceleration, a clunk when changing between drive and reverse, oil leaks near the pinion or axle seals, or vibration through the floor when towing or under load. If you notice metal flakes when changing the diff oil, book an inspection immediately.
Most 4WDs benefit from an oil change every 40,000–50,000 kilometres, but it’s wise to do it sooner after water crossings or extended towing. The correct oil grade varies between models, so always check your owner’s manual or ask your mechanic.
A service involves draining and refilling oil, checking breathers, and inspecting seals.
A rebuild is more extensive — the differential is removed, stripped down, worn parts replaced, and gear clearances reset to factory specifications.
You can, but it’s risky. The longer you drive with a whining or clunking diff, the more damage spreads to the gears and bearings. In severe cases, the diff can seize or fail suddenly, leaving the vehicle immobile.
Yes. The workshop rebuilds standard, locking and limited-slip differentials using OEM or performance-grade components. Each one is set up using precision measuring equipment and tested before refitting.
Most rebuilds take two to three business days, depending on parts availability and the condition of the unit. Each job is bench-tested and road-tested to confirm quiet, smooth operation.
