hi I've had my 8 for 10,500kms now and ever since around 8000km I've started to notice that the engine sounds kinda rough at low-mid rpms. At first I thought this might be me needing an oil change but after the 8000km service it still had that same sound and it started to get worse.
so today I changed the transmission and differential fluid and wow what a difference it made! I admit I scraped 3rd and reverse gear once or twice before but I didn't know it made so much metal particles to make that sound (turns out it was my transmission that making the rough noise). and it also helped get rid of some of the roughness in shifting as well and my gear shifter slides into each gear like it was in the showroom again!

so I highly recommend those ppl who didn't get their fluids changed at 5k like some members here did to do so asap