If the ATF is low or has clutch friction material in it the box will change quite hard when hot.
Do the revs flare when trying to change from 3rd to 4th? What happens when it is in Tiptronic mode?
Sounds like K1 clutch is burning/burnt out. You can buy all the parts separately,even the solenoids. http://www.sussexautos.co.uk/onlinec...%2009K,%2009M)
I've been doing a bit of research on this. It looks like the transmission valve body (mechatronic unit) is on its way out. It's a common fault on the older Audi/VW tiptronic and multitronic gearboxes. Apparently Audi in America have extended the warranty on this part to 100,000 miles as it's a known issue, but no such cover here. Do a google search for 'valve body fsi automatic jerk' and you'll see dozens of websites about the problem. If it is this, it's a four figure sum to fix.
Car is booked in with Audi tomorrow. Will let you know how it's got on. Fingers crosses
had it in at audi on friday. they spent 5 hours on it and basically told me that they cant get to the root of the problem just yet because i need to change my catalytic converter because its basically had its day and its throwing up many error codes. luckily they didnt charge me anything but just said bring it back when you have the new cat on the car. so il be doing that in the coming days. il update as soon as.