Hello everyone, back again with another issue. I picked up a rather nice 1983 XJ6 Vanden Plas, but on my drive home with it, I noticed that it wouldn't register any speed higher than 20 MPH. As I understand it thus far, when the transducer fails, you get nothing. So that's clearly not the case, which brings me to the point of my post here, where do I look for the failure? At 45 MPH, my speedometer reads 20, maybe 21 MPH.

 

No, the transducer can fail in multiple ways. Yours probably needs replacing.

The only other choices are the wiring and the speedo itself.

Used speedos and transducers are inexpensive from Everyday XJ. New transducers are about $100

You can check wiring continuity as well as connections at the back of the speedo before buying any parts.

Cheers
DD

 

Thanks Doug, I've got a spare speedometer, and possibly a spare transducer if the 6 cyl and 12 cyl cars use the same transducer. I've found myself with a curious habit of raiding everything off of junkyard cars I come across due to their scarcity in my area.

 

12 cylinder transducers are different

Cheers
DD

 

Is that what you told the officer who nabbed you for speeding??

 

I got tired of the speedometer problems and went with this 4-1/2"GPS Speedometer Gauge 160mph (w/ turn signal and high beam) / SKU:GR4.5-GPS-03T from SpeedHut. You can choose the options you want and they workgreat. I also went with the matching Tach. I can post a Pic if anyone isinterested on how they look. These eliminate the need for speedo cables, transducers and any otherpain in the but parts.

 

The transducers ARE different. I used a V12 XJS transducer on my XJ6 6 cylinder to Chev V8 with 700r4 trans swap
The Jag V12 transducer can be screwed into the GM speedo system (700r4) because the type of threads on the V12 transducer, are the same as you would find on a typical GM trans - The V12 uses a GM trans and a transducer sending an 8000 ppm signal to the Jag speedo, cruise, trip computer. For my GM swap I spliced in a VSS unit sending 2000 ppm to my EFI ECM and I end up getting 2 different signals coming from the GM trans speedo output and at the same time and kept the Jag speedo system intact and the GM EFI ECM happy.