Coding Plug 5spd swap question

[GT BMW E30]

Should I swap the coding plug in speedo when doing a 5 speed swap and changing diffs to 3.91?

[The Dark Side of Will]

No. The VSS is on the axle, so diff ratio doesn't matter.

[nando]

yeah, the coding plug has nothing to do with the speedometer.

All BMWs use a 9 tooth wheel in the differential with a reed switch that generates a sort of square wave of your speed (pretty much until they switched to using ABS for speed input), which is what the cluster uses. Doesn't matter what diff or trans it is.