S tronic help, reversing

[moxy89]

Couple of months ago I purchased a low miles Audi s3 s tronic 62 plate, car has done 1000 miles in nearly 3 months and it's been perfect, today I reversed off the drive, gave it a small amount of throttle and a horrid rattling appears, if I reverse the car without any throttle no noise at all. All the drive gears are spot on, I really hope it isn't a new box time! Anyone had similar issues ?