Can anyone tell me how many teeth there are on the tone wheel for diff mounted speed sensor pickup? I'm looking at using an XJS trip computer on a different car with an XJR powertrain and want to make sure the distance data is correct.

Unfortunately, the XJS electrical guide doesn't help, and all it says under output is "AC volts increase with road speed". The X300 guide tells me the specific frequency for a given road speed, I was hoping to find that data for the XJS.

I have also looked at the XJS parts book and don't see the tone ring listed. Everything else inside the differential is called out, but not the part the crown wheel would bolt to: Final Drive Unit Components - Parts For XJS from (V)179737 to (V)226645 | Jaguar Classic Parts UK

 

I haven't this information published anywhere. But I do believe the XJS uses a frequency to voltage converter. Where the output of the module is a DC voltage proportional to road speed.

The reluctor ring is part of the diff center unit and not separate like the ABS rings on the wheels.

You could test your XJS by measuring the output voltage of the speed module at 3 road speeds 10, 50 and 100km/h assume the curve is linear and use these voltages.

 

I may have to do that. Or I could assume it's the typical output Jaguar has used in the past of 8,000 pulses per mile and see how close that is if I put that signal into the trip computer.

 

This guy has worked out the details of the XJ6 trip computer

Jaguar XJ6 SIII trip computer details

 

I have seen that site before. I'm using the later generation of trip computer though.

I have done a test with the XJR instrument cluster on the seat and a wire run to the XJS's trip computer fuel signal and they each show the same total amount of fuel used, so that is encouraging that the fuel used pulse is the same between the XJS and XJR.