The quattro badge is one of the hallmarks of Audi engineering. Introduced in the early 1980s, it helped bring all-wheel drive out of the world of off-roaders and rallying and into sporty road cars, changing the way we think about grip and safety. Behind a now-familiar name, however, lies a technology that has changed considerably over the decades. Understanding how it works helps you better assess a used Audi, especially one that has been imported and reconditioned.
What quattro drive is
quattro is the commercial name Audi uses for its all-wheel drive systems. The goal is to distribute engine torque across all four wheels, rather than to the front or rear axle alone. This way, the power delivered to the ground makes use of the grip available on more tyres, with clear benefits on slippery surfaces, under acceleration and through corners.
One clarification is needed, though: different technical solutions live under the same name. Not all quattro systems are the same, and the difference depends mainly on the engine architecture (longitudinal or transverse) and on the type of centre differential.
The centre differential: the heart of the system
On Audis with a longitudinally mounted engine (typically the A4, A5, A6, Q5 and models above), the key component is the centre differential, which splits torque between the front and rear axles and allows the two sections of the drivetrain to rotate at different speeds, for example when cornering.
From the Torsen to the crown-gear differential
For many years Audi used the Torsen differential (from the English Torque Sensing): a purely mechanical limited-slip differential. When one of the two sections starts to lose grip, the Torsen automatically transfers torque towards the axle with more grip, with no electronic intervention.
Audi later adopted, on various models, the crown-gear centre differential, likewise limited-slip and mechanically controlled, but more compact and lighter and with a wider torque-transfer capability than the Torsen.
The multi-plate clutch on transverse-engine models
On Audis with a transverse engine (for example several A1, A3, Q2, Q3 and TT variants) the layout is different: here all-wheel drive is managed by an electronically controlled multi-plate clutch, which engages the rear axle when needed. It is an on-demand solution: under normal conditions the car runs mostly in front-wheel drive and torque is sent to the rear axle based on sensors and control strategies.
Torque distribution
In systems with a limited-slip centre differential, the baseline split is not necessarily even: on more recent models Audi generally quotes a rest distribution biased towards the rear (commonly cited around a 40:60 ratio between front and rear), to encourage dynamic, neutral handling. In case of wheelslip, the differential can shift a significant share of torque towards the axle with more grip, continuously and automatically.
In multi-plate clutch systems, by contrast, the split is more variable and depends on the electronic logic, which can shift quickly from a front bias to a more pronounced rear contribution.
Permanent quattro and quattro ultra
This gives rise to the most useful distinction for an enthusiast:
- Permanent quattro: with a mechanical centre differential, all wheels are constantly connected to the drivetrain. The response to grip transfers is immediate, because the differential itself redistributes torque mechanically.
- quattro ultra: a more recent version designed for longitudinal engines, prioritising efficiency. The system can decouple the rear axle when it is not needed, reducing friction and fuel consumption, then reactivate it predictively thanks to the electronics. A similar on-demand philosophy characterises the transverse-engine models with a multi-plate clutch.
In short: permanent quattro relies on mechanical continuity; quattro ultra and clutch-based systems seek a balance between traction and efficiency.
The advantages: grip, safety, stability
Beyond the technical layout, the benefits that make quattro so valued are consistent:
- Grip under acceleration, especially on wet asphalt, snow or low-grip surfaces.
- Stability through corners and during changes of direction, thanks to better management of load transfers.
- Active safety, because distributed drive reduces the risk of wheelspin and works in synergy with the electronic stability controls.
It should be remembered, with due caution, that all-wheel drive improves traction but does not repeal the laws of physics: braking distances and cornering grip still depend on tyres, road surface and driving style.
Why the quattro system matters on an imported, reconditioned car
A quattro system is only as reliable as its maintenance. Differentials, joints, the multi-plate clutch (where fitted) and their oils require periodic checks: degraded differential oil or a worn clutch can compromise torque distribution and how the car behaves.
For this reason, on the Audis we import from US and international auctions, checking the all-wheel drive is part of our 47-point inspection process. In our workshop we check the condition of the quattro system, the drivetrain components and the fluids, fitting OEM parts where necessary. The outcome goes into the technical dossier signed by the Chief Mechanic: this way the buyer knows exactly the condition of one of the components that most defines an Audi. It is how we translate our idea of transparency into verifiable data, valid for the Italian market just as much as for the Romanian one.