there is no need to undo the speedo cable from the gearbox if u can get 2 fingers behind the cluster.
if there is room reach behind the cluster from the left and u will feel a round shaft protruding from the back of the cluster, there is a clip that undoes itself when u press the top of it. usually a bracket holds the speedo cable to the frame of the dash so unscrewing it from the gearbox may not work.
if u need to visualise here is some bad ascii drawing...
clip press it``` |
````_ _ _ _```|
---/```````|----|
speedo cable``| back of cluser
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