So today I removed a 4.1 open diff originally fitted to a 91 320i .
I then fitted a 3.64 lsd that was in an e36 compact.All went well until the end where the half shaft bolts are a different spec.
The placement and spacing of the 6 bolt holes on each side of both diffs is identical.But only after fitting the new diff I discovered the new diff bolt holes are slightly narrower so I couldn't compete the job meaning I'm feckin car less until I get this sorted as I don't want to undo all that work today.
I think it is the cups. Picked up cups and shafts today from a 325 so hopefully get sorted when I get back at it....it's in a different county now as I wasn't gonna refit the old diff again to get home. One of the top bolts was a complete pig.