Well I've done it I've changed out the balancer shaft on my car before i had any problems as a preventative measure and I'm so glad i did. The part that came out of the car wasn't so worn but the hex shaft was so loose in the banner shaft I could see it going at any point. I'll include some info so other people searching and deciding if to do there cars can read the info for future reference. All I will say is if you haven't changed the balancer shaft yet DONT bury your head in the sand it is VERY likely to fail and better to replace it before it does real damage to your car.
My car is a 2.0 ltr TDi registered in 2008 after doing research i found out that its a gear driven balancer shaft. The chain driven were only installed for a brief period up until 2006 so I'm lead to belive.I phoned my local Audi to confirm what type my car had installed from factory and they advised me after looking into the service history of my car that it did indeed have the gear driven Balancer shaft.
I then contacted Graham at KMB parts and spoke to him at length about my car and he also confirmed that my car had a gear driven balancer shaft. I ordered kit 9 from KMB at a cost of £225 plus £125 deposit which i got back once I returned my old balancer shaft as they offer an exchange service. Graham was really helpful and knowledgeable and I had the balancer shaft by the next day.
Pictures and video below of the new remanufactured balancer shaft
video of the new balancer shaft (sorry for shaky camera but shows secure fit of new part)
old balancer shaft taken out of the car
Video of the old balancer shaft out the car you can see the loose fit of the hex key and the short distance it goes in
My car had the longer 77mm hex fitted as standard but as you can see from the video there is a lot and I mean a lot of movement from the hex shaft in the balancer shaft so although at the old hex shaft doesn't look too bad I'm sure it was only a matter of time till it went and i saw the dreaded red oil light.
I am really pleased that i decided to do the preventative measure and can now rest easy knowing there is a far superior part fitted into the car.
the garage charged me £350 labour to swap the parts over so the whole lot cost me £575 which i think is quite cheap for piece of mind. Its just a shame us Audi drivers have to foot the bill for this poor design and not Audi themselfs.
Once again don't bury your heads in the sand hoping it goes away bite the built and get it changed. Not just the Hex key but the whole balancer shaft as its the poor design and manufacture of the keyway in the balancer shaft that causes the hex key not to engage securely and eventually round off.
Just want to say Thank you to everyone who has helped and commented while i was researching this.