40 pulse vss to 1986 XJ6 speedometer

[BobPhx (Bob Brackney - 89 XJS V12, 5 sp/Marelli | 2013 XKR)]

GPS Speedo Solution

When I installed an older IRS center section, to get a 3:54 ratio in preparation for my five speed upgrade, I lost my speedometer as the older units have no provisions inside the diff for speedo sensing. I expected this, and I had a few different ideas on how I might regain speedo function. Swapping to an older transmission /electric driven speedo set up was the least attractive option. My first thought was to have the speedo head rebuilt to be GPS driven. After some research, I learned that …