Salut Gayo! Mon ami en le pais de fromage e vin rouge!
I just found an Astro setup from the Durango web page - and it works great for me. Haven't tried different settings (not felt the need). I've seen Hupo take out one of the internal set of gears, probably to make it even more free (haven't tried). It feels very similar to the ball diff. And is quiet. My Durango OTOH is a noisy bugger (seems to be a problem with the center axles, something came bent in the box - will try and buy new parts).
Blue_Pinky, I know the B44 very well. And I never had this problem on other types on tracks for years. Even the first astro tracks. But my local track is just super grippy. I always shim them as tight as possible. And use as loose a slipper as I can... still goes... a guy I regularly practise with experiences the same. Metal gear diff seem to just go on and on, and they stay super smooth. Whilst the ball diffs really take a beating on astro, and get notchy quite fast.