Title: Sudden lost of traction at rear axle at high way speed. Vehicle mileage: 40,000; age: 5 years; AWD model with rear electrical differential power coupling (haldex gen 4 ) description: Vehicle was driving at highway speed, dashboard shown message: "transmission fault traction reduced". the rear axle was found to be disconnected from drivetrain and will not reconnect under slippery condition. Root cause: Rear electrical differential (haldex gen 4) use pnuematic controlled clutches to connect/disconnect rear axle to transmission for torque coupling. The clutch relies on pnuematic pump (Land Rover part number LR075763) to provide pressure for coupling. The pump use brushed DC motor. Overtime, clutch material dissolve into differential fluid and clogs up filter of the pnuematic line, causing pump running at high duty cycle. The motor failed due to excessive heat and brushes disconnect from motor winding. Causing pump to fail. For reference, Volvo and othe vehicle manufacturer who use similar differential unit (haldex gen 4) requires servicing of the differential to prevent such failure. Land Rover does not such procedure. Land Rover has tsb that describes such failure and mentioned the pump will need to change. Https://static.NHTSA.gov/ODI/tsbs/2015/sb-10074556-2280.pdf

- Sunnyvale, CA, USA