Turbo 400 box in vh speedo not working

[budgieVH]

Hey guys just brought a vh with vs 5ltr and turbo 400 gear box and the speedo is bouncing all over the place.

What could it be?
speedo cable?
Cluster??

need to fix it for a road worthy

[drewVHSS]

sounds like where the cable inner mates into the back of the speedo input is slipping or is worn.
My SS does it too.... try re-seating the cable and see if the inner hasn't slipped back away from the speedo. Sometimes getting a better approach angle with cable helps too.