Viscous Coupling
A viscous coupling uses thick silicone fluid between plates to transfer torque when one side turns faster.
What is Viscous Coupling?
It is used in some AWD systems and limited-slip differentials. It works automatically without electronics. Older designs have been replaced by electronic clutches. The fluid can harden or lose properties over time, so the coupling may lock too much or too little. A simple test is to lift one end of the car and turn a wheel by hand; strong resistance can indicate a seized unit. Matched tyres with even wear help prevent overheating.
How it works
Speed difference shears the fluid, which thickens and transfers torque.
Why it matters for your car
A seized coupling causes tight steering in corners and tyre scrub. Mismatched tyre sizes can overheat it.
Other terms
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- Brake Bedding-in
- Brake Force Distribution (Brake Bias)
- Bump Stop
- Cylinder Head Skimming (Resurfacing)
- Diesel Fuel Heater
- Driver Fatigue
- Exhaust Backpressure
- Ignition Switch
- Intake Air Temperature Sensor
- Leak-down Test (Cylinder Leakage Test)
- Mechanic’s Stethoscope
- Parking Pawl
- Power Band
- Preconditioning
- Seat Adjustment
- Torque Vectoring
- Tyre Patch Repair
- Water Pump
- WLTP (Worldwide Harmonised Light Vehicles Test Procedure)