How to fix a Flaky Speedometer on XJ6 Jaguars
The speedometer operates from a signal generated by the transducer. The transducer is screwed into either the tail of the transmission, or into the differential, depending upon the year and model of your Jaguar. If your speedometer works, then doesn't, then works again, it's usually the transducer. Clean and tighten the electrical connections at the transducer, and if that doesn't work, then it's time for a new one.
See our Jaguar Parts Store Catalog to order parts.