transit speedo module faulty?

[graftergav]

hello to everyone this being my first post, i have a r reg transit lwb high top 2.5di and as the speedo was fluttering up and down have changed the clocks for another set only for the fault to continue, the speedo is the elctronic type so i would assume the sender unit is at fault? does any one know where this is located? or had the same trouble as this? or knw how to fix it? any help or info given would be great. thanks gav.

[ake]

Speedo sender is a the prop end of the gearbox iirc