Diff/speedo problem

[Ferret]

Hi,
I swapped my 3.91 small case diff's center section from an open one to a limited slip unit.
Since then the speedo stopped working.
I suspect that there is a difference in the toothed wheels that are attached to the center sections which drive the speedo sensor.
Anyone knows how I can get my speedo back?
Thanks,
Avner.

[PiercedE30]

switch the other sensor maybe?

[Ferret]

I don't have the other sensor, I bought only the LSD center section (without the case etc.).