[bangles]

Hi I have a 03 velsatis 3.0dci auto, when i put it in reverse somtimes theres a juddering other times its ok was told that it was the gear box and got quoted £3000 to replace i then had a diagnostics test and was told "no fault on the gear box its a nuteral circuit switch and clutch circuit switch could anyone tell me exacly what this is because everyone i ask has no idea thanks maria