172 mk1 speedo going nuts

[RichMcc]

I was driving to work and my speedo started to go nuts, dropping to 0 then shooting back up to what ever speed I was doing. 0-60 in less than a second!!!
Then it died all together :dead:
Then it came back!!!!
Then it died again....
It just sits on 0 most of the time but occasionally kicks into life before dying again.
The dial test works perfectly and the needle moves but nada when Im driving.


Anyone? :S

 

[edde]

The speed sensor on the gearbox is most likly come loose.

 

[RichMcc]

where abouts is it mate?

 

[16v_jon]

back of the gearbox next to the gear box earth point