Transmission & clutch · Sant Andreu
Differential: diagnosis and repair
A whine that grows with speed, oil dripping from the rear casing or a clunk on and off the throttle: the differential warns you with sounds. Honest diagnosis and repair with quality parts.
What does this service include at Tallers Marathon?
Diagnosis of the noise or play, seal and gear oil replacement, and repair of the unit when damaged.
- Noise diagnosisWe distinguish differential from wheel bearings or tyres: they sound alike.
- Seals and gear oilA gear oil leak is the no.1 avoidable cause of differential death.
- Unit repairBearings, crown wheels and planetaries with correct preload adjustment.
- 4x4 vehiclesFront, rear and centre differentials, and their couplings.
What does a failing differential sound like?
A dull whine that grows with speed and changes on and off the throttle, or a metallic clunk when the load reverses. If the whine varies in corners, the suspect is usually a wheel bearing, not the differential: the road test tells them apart.
The differential is one of those parts nobody remembers until it makes noise, and its maintenance is absurdly cheap compared with its repair: gear oil at the right level with no leaks. The failure pattern we see: a seal starts weeping, drop by drop for months, level below minimum, and the unit running dry until it whines. A glance underneath at every service prevents it. In loaded vans and 4x4s that tow, the gear oil also runs hotter and deserves renewing by interval even without leaks. If the clunk appears on and off the throttle, we also check the mounts and driveshafts, which share the symptom.
Frequently asked questions
How often is the gear oil changed?
On rear-drive cars and 4x4s, roughly every 60,000–100,000 km or per the manufacturer; sooner with towing or intensive use. On many cars nobody has ever touched it: that is the problem.
Can I keep driving with the whine?
The whine only gets worse and the ending is a locked or broken unit. Early diagnosis keeps the cheap options open (bearings, preload) that time closes.
Do you repair 4x4 differentials?
Yes: front, rear and centre, including Haldex-type couplings and their oil-and-filter servicing — another great forgotten item.
How do I know the stain on the floor is the differential?
By position and colour: gear oil is thick with a strong smell, unlike engine oil. On the lift, the exact seal is located in minutes.
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