A normal phenomenon… on dry roads
When cornering, the front wheels travel a greater distance than the rear wheels. On a part-time 4x4 (button or lever), front and rear are locked together: the drivetrain binds, and at low speed the car judders, hops or fights against full lock. This is how the system is designed to work, but it should only be used on slippery surfaces.
On dry roads, disengage the 4x4. If the juddering disappears, no component is at fault.On a permanent or automatic 4x4
Permanent systems (xDrive, 4Matic, quattro…) use a centre differential or a controlled clutch to absorb this difference. If they judder on full lock, the causes lie elsewhere:
- Tyres of different diameters between front and rear.
- Worn or incorrect transfer case oil, causing the internal clutch to grab.
- Worn internal clutch in the transfer case.
The risks of leaving it unchecked
Driving with the 4x4 engaged on dry roads, or leaving a permanent 4x4 to judder, places considerable stress on the driveshafts, axles and transfer case. Wear accelerates and can ultimately lead to component failure.
What should you do?
On a part-time system: only engage 4x4 on slippery surfaces. On a permanent system: fit four identical tyres, drain and refill with the recommended oil, then carry out a diagnostic relearn. If the internal clutch is worn, a reconditioned transfer case on an exchange basis will resolve the problem for good.
