Sensor on Manual Gearbox/Transmission

[clubman22]

Hi, My 2010 2.0 TDI A4 is hitting high mileage and I have it with my local garage to swap in a second hand gearbox from a breakers yard. The original gearbox (that is coming out) has a sensor/switch in the gearbox housing to the left had site of the gear lever. The gearbox to be swapped in does not have this. I cannot find out what this does and if it is important. Does anybody have any ideas ?

[Crasher]

Wrong box then, there is bound to be much more to it than a switch. PM me the reg or post the VIN and the three digit code off of the new box. I have said it before and did it to myself last year, used boxes are often a disaster.