With regard to the 14 toothed shaft, I understand this has to be fitted with a degree of backlash to prevent the gearbox drive from stripping the teeth from the driveshaft. The only way I and can see to get the backlash and freeplay is if the cast brass ferule which retains the shaft, and is inserted and clamped into the gearbox, is not fitted fully home?
Is this correct?
Any guidance would be welcomed as I would prefer a working speedo and not another shaft with no teeth!

My bus number (if any): RM531

The housing has notches in its outer edge. Release the clamp and rotate the housing to alter backlash. Rotating the shaft will reveal the amount of backlash. The notches allow the amount to be easily visible.

Thankyou Roy. With the housing properly cleaned up I have just found the notches-4 on the top and 5 below. The housing is an extremely tight fit in the gearbox and required some persuasion to remove- with the clamp loose should it turn easily? How much backlash would you advise?
Thanks for your help, it is appreciated.

My bus number (if any): RM531

The housing should be free enough to rotate it by without having to use any tools. it is impossible to describe how MUCH backlash to set since it is a feeling. Look at the size of the teeth meshing and allow a little rotational free play. Use the notches as a guide.

Speedo now working perfectly. Thanks Roy, much appreciated.

My bus number (if any): RM531