the aftermarket Diffs for auto 135i's i think work in 128i manual- look at wavetrac part number for 128i
Not sure about Auto 128i
Qualife makes 128i stuff and so does Wavetrac
i think Wavetrac is the cheapest LSD
e90 N52 guys also swapped other e90 diffs, but its not a real diff...
128i Sport 6MT converted to Euro 130i spec, tuned by evolve ~220 whp 207 wtq(ft-lb) SAE
In-progress: e46 m3 trans mnt, e36M lip Wishlist: m3 susp, n55 eng mnt, headers, LSD, finn dif e60
"The 1-series is the last car that BMW engineered before the Germans, as a car-making culture, fell out of love with driving." - R&T 2013 135is