Disco 2 auto limp mode

Hello, I have a disco 2 td5 auto 2003. Gearbox goes into limp mode shortly after setting off. Symptoms being; lots of revs to get car moving (coz in 3rd i guess), can put car in 1,2,3 or D and no difference. Red lights on gear stick go off (m&s lights on dash never worked). Loud clunk from gearbox moving in/out of D & R. Garage tentatively diahnosed xyz switch or chafed wiring loom shorting. Not been on computer yet! Car booked in for next thursday and just wondering whether any damage is going to be done continuing driving. My wife uses motorway for one junction so assume she will be limited to 3rd gear speeds. What is the max speed or just listen to engine? Thanks

Better don't drive it this way, that's why it's generally named "limp home mode", to get you home from where you are and then fix it, there can be 15 reasons for that even though the XYZ switch is the most common, and if it's some other valve block thing which can restrict the oil pressure you can ruin the box for good, if the warnings never worked you might have had flashing M & S prior of this too without limp mode as a start of the fault and the things just got worst in time... i cant understand why you didnt fix that warning light first and just kept driving it so though ...