I've got a '96 Defender 110 2.5tdi. Out of the blue, having been parked (in the cold, Austria) for a couple of days, the gears wouldn't engage anymore in normal drive; they only work with the differential locked. The dif-lock light seems to go on and off pretty much at will and there is also a metalic click when I take it out of 5th (engine off). Stranded in the driveway!