The Land Rover Disco is not permenant 4x4......it is switchable rear wheel drive and 4 wheel drive hi and low ranges.........it hasnt got the viscous couplings of the Range Rover and cant tolerate being on tarmac unless its in 2wd setting, if you run a Disco in 4x4 on the tarmac you will suffer torque wind back and will snap half shafts in the axles or rip the splines out of the diff..........this was true for anything older than the new shape which may still be the same transfer box as i know very little about the recent face lifted versions.