Read around forums for awhile and havent found any posts mentioning this issue.

So I bought a 2001 audi tt 225 quattro. Tachometer kind of fluttered at high rev but other than that nothing. Speedometer would start off fine but would drop 10mph at a time till reaching zero, then would work fine again from dead stop till it fell to zero again. Odometer worked fine, bat was fine, fuses fine, no codes, etc etc...

Investigate at your own risk, only stating my experience and solution.

Pulled out the gauge cluster and disassembled. Each of the needles are run off a clear plastic case motor snapped on the back of the board. After removing these two motors and carefully seperating the case, I found three gears. One gear was mounted to the top of the magnet of the motor brown in color. Second gear is a reducing gear, greenish. Third gear is mounted to the pin that drives the needle, white. The second gear, the reducing gear, is mounted on a plastic pin molded onto the motor case. Both the tach and speedo had these plastic pins sheered off the motor case allowing the reducing gear to float freely and not mesh properly. Due to the tight case, the gear stayed in its location, and would mesh occasionally, but not always.

My fix to this without ordering the same junk parts.

Please research a gauge cluster removal and disassembly guide before attempting to do this. There is one out there, ive seen it, and you will probably ruin your cluster if you dont.

Once you remove the faceplate to the gauge cluster, TAKE A PICTURE OF THE NEEDLE LOCATIONS. If you dont you will have a fun time resetting them.

I took a drill bit that matched the outside diameter of the pin that had sheered off and made sure it fit the second gear freely but not sloppy. By hand, i carefully spun the drill and drilled a hole through the plastic with the drill IN THE EXACT LOCATION WHERE THE PIN WAS SHEERED FROM. Not drilling the hole in the same exactly location almost perfectly will affect your gear mesh and the motors will not work properly. After making the hole, I test fit the back of the drill bit(not the drilling side, the otherside lol) into the hole in the motor case and through the gear to determine the length i would need. I made it just below surface of the face of the gear. Once I knew my length I used vise grips carefully to break the length of the back of the drill bit I needed. It was roughly 3/8ths long if I remember correctly. I used a grinder to make a few small notchs at the very tip( no more than the thickness of the motor case I would be gluing to) of the new shaft to allow the epoxy to have a rough surface to hold to. I carefully applied a small amount of epoxy to the notched part of the shaft(not alot you do not want any of this glue on the shaft where the gear spins or inside the case where the gear sits). I pushed the glueless portion of the shaft through the outside of the motor case to the inside so when I pressed it flush to the outside of the motor case, no glue would enter the inside of the case. Before the glue dries, place the gears back into the motor case without the loaded return spring. Try to spin the needle (the white gear has end stops, it will only spin so much one way then stop, do not break these end stops), it is kinda hard but you can rotate the pin with your fingers. If you cant, then your gear mesh is off and you will have to tweak the new reducing gear shaft to ensure the reducing gear sits properly in relation to the two other gears. Be sure they all mesh and spin. Once gear mesh is correct, allow for some dry time. Side note, the sheered plastic pin is on the side of the case that will sit flat against the cluster's board. You can not have any of this pin sticking out past flush with the outside of the plastic motor case or the motor will not sit flat and the rmp/speedo needles will drag. Disassemble the motor again and carefully put the spring back in its home in the motor case, ensure you are preloading the spring in the proper direction. The spring is to help the needles return to zero, so kinda hold it up to your cluster and understand which way the needle will spin for rising speed or rpm, so since your rpms raise in a clockwise rotation, it will return ccw. So, place the spring in, set the white gear in the case over the spring, and lift it up slightly, spin it slowly clockwise and be sure it grabs and spins the preload spring without popping it out of its home. I preloaded mine two full rotations and I think 3 to 4 preload rotations will allow the needles to return home quickly. Youll know if you went too far with the preload, the needle will go so far and stop when you start the car. I think with 6 preload rotations, my rpm would stop just before 4k rpm. Once preload is set correctly, place reducing gear then magnetic gear in front motor case with the white gear and carefully put the back of the motor case on. Even with the needle preloaded you should be able to twist the needle. It may not return to zero on its own with the spring load, mine doesnt and works fine. Once you are pretty sure they are working, reconnect them to your board, and place your needles back in the zero position you took a picture of. At this point I reconnected to the car carefully and used live data feed from a scanner tool to be sure my speedo and tach were reading correctly. You can fully reassemble it to test it but its up to you.

Or

Buy new motors for the board and swap them

So ya hope this helps somebody somewhere with wierd cluster issues

Show Me Them TTies!