Differential speed sensor trigger surface

I couldn’t find the thread, but awhile back there was some discussion about what exactly inside the rear diff triggers the speedometer sensor (on cars equipped with the diff-mounted sensor.). Here’s the answer. Newer diff (89 xjs) has a machined surface that lines up with the sensor. Older diff (red, 69 E type) does not. These are both Salisbury diffs. I’m installing the red one b/c it has the 3.54 ratio I want for my manual conversion. I’ll likely convert my speedo to gps.

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Y’know, you could fake that pickup. Fashion a piece of sheet metal to replace one of the shims between the output shaft flange and the inner U-joint on one side. At the OD of this critter, cut a series of teeth, making sure it’s the same number of teeth as on that carrier on the inside. Then fab up a bracket to hold the OEM pickup near those teeth.

Interesting. I had not thought of doing it externally. If you could get it to turn true enough you could drill however many evenly spaced holes in the sheet metal ujoint shroud. The “bars” between the holes might trigger the pickup.

The uni shroud might move about too much for the sensor. Kirby’s idea is on the “solid” side of the joint so no moving with suspension. Air gaps are normally pretty sensitive.