Mark,
When my speedometer was not working I found the gearbox was assembled with no worm drive fitted.
This would obviously have caused problems as it acts as a spacer on the gearbox shaft.
On investigation I found there there were variations on how many starts there were on the worm and also how many teeth on the pinion. I had an 8 & 9 tooth pinion available so fitted the 9 tooth pinion and single start worm.
They appeared compatible but The Speedo shows about 30mph, the satnav reads 40mph.
There is an article in the BA7C somewhere I believe about speedometer drive gearing.
Roger
When my speedometer was not working I found the gearbox was assembled with no worm drive fitted.
This would obviously have caused problems as it acts as a spacer on the gearbox shaft.
On investigation I found there there were variations on how many starts there were on the worm and also how many teeth on the pinion. I had an 8 & 9 tooth pinion available so fitted the 9 tooth pinion and single start worm.
They appeared compatible but The Speedo shows about 30mph, the satnav reads 40mph.
There is an article in the BA7C somewhere I believe about speedometer drive gearing.
Roger
Location:- Haverfordwest, Pembrokeshire.