Looking for a bit of advice.
I have a XF Ute which the previous owner fitted a wagon diff to. The speedo now reads slow (according to Mr Plod). The wheels have also been changed to the 15" Ghia mag wheels. MY question is what do I have to do to get the speedo to read correctly so I don't inadvertantly speed?

find out the diff ratio you have, and work out what speedo driven gear you require.

Most likely you could get an off the shelf item.

but we need more stats to help!

Try this, I think this will help you, documents.php?d=30