So I just got my first 5 speed a4 and when driving on the interstate at about 80 it feels like it could use another gear. It sits at about 3500 rpms and feel like another gear could really help it run closer to 2500-2800 and get better gas mileage! I have done a little research and looked around and I know the 1.8 TT Quattro has a 6 speed and so does the '04 A4 1.8T Quattro. Would this fit on my 03 A4 1.8t? Has anyone either done this or heard of someone doing something similar?

 

I thought exactly the same as you when I first got my 2003 A4 3.0 cabriolet. I do believe that after 04 models of the A4 they started putting 6-speed boxes in these cars so I wouldn't see any problems in fitting a 6-speed, if you can get hold of a decent one.
I wanted to get mine converted but after looking around I felt it would be cheaper to sell mine and buy a 6-speed however I haven't done so yet as I have got used to it sitting slightly higher on the rev range.

Another thing to note is that I think all Audi's are like this as I drive a 59 Plate A5 Cabriolet 2.0T Auto and it also sits at 3000 RPM at 70 MPH.

 

Both your gearing/RPMs are correct for the speeds. They are meant to be like that, you get used to it after awhile, that's why they are so quick. It sounds and feels like the RPMs are too high, but that's how they are geared.

 

yeah I am already starting to get used to it but it was just my initial impression on the drive home when I bought the car. I spent a lot of time in the 75-80 range and just felt it was bit high. This is my first 5 speed manual car and I knew it obviously wasn't going to run at 2500 like my brothers avant. I will continue to get used to it and find other ways to increase my mileage lol. Im thinking about going with a chip to bring it up a bit (im kind of a mpg junkie) haha