Hello,

I have a BMW E21 3.91 differential LSD to put on my BMW 2002 72. As I determine the % of lockup of the differential??
I don't know if is 25%, 40% or 70%. The aluminium cover has a tag with
"S 3.91 9901" code.

Thanks

Fernando

Unless it has had different plates, or ramp angle changed, the lockup is 25%