Mechanic & Differential Repairs for Angle Park

This page covers the differential, which is the part of the driveline nobody thinks about until it makes a noise, and by then it has usually been making that noise for a while.

A differential lets the driven wheels turn at different speeds while still receiving power, which is what allows a car to corner without dragging a tyre.

It does that through gears running in oil, under high load, with sliding contact rather than rolling contact on some surfaces. That combination is hard on oil. Diff oil shears and degrades, and unlike engine oil there is no filter and nothing to catch the metal it wears off.

A mechanic Angle Park drivers use should be checking diff oil condition on any rear-wheel-drive or all-wheel-drive vehicle past about 100,000 km, because it is one of the most commonly skipped items in servicing.

A whine that changes when you lift off the accelerator. Classic diff. Under power the gear teeth load one way, off the accelerator they load the other, and worn teeth or an incorrect mesh sound different in each. That change is the identifying feature.

A rumble that rises with road speed regardless of throttle. Usually a bearing rather than the gears.

A clunk when taking up drive. Excess backlash between the gears, sometimes the diff, sometimes a worn universal joint or driveshaft coupling ahead of it.

Chatter or shudder on tight low-speed turns. On a limited slip diff, that usually means the friction additive in the oil has worn out. Sometimes an oil change alone fixes it.

Diffs use pinion and axle seals, and both harden with age. A weeping diff is not dramatic, and it is worth attending to, because there is not much oil in there to start with. Running one low quietly ruins the gears, and a diff rebuild costs many times what a seal does.

Look for a wet film on the diff housing or oil thrown along the inside of a rear wheel.

• Check the oil level and condition, not just the level
• Look for metal in the oil, which tells you how much life is left
• Inspect pinion and axle seals for weeping
• Check backlash where a clunk is reported
• Confirm the correct oil specification, including friction modifier on limited slip units

2/208 Grange Rd, Flinders Park, about six minutes from Angle Park. Bring it in early if it is whining, because a mechanic Angle Park drivers trust can often save a diff that is only just starting.

Call (08) 8443 7900.

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