The 'E' Type Forum

Does anyone know what the ratio is between the speedo driven gear and the driveshaft?

I get 1 revolution at the speedo cable for 2 revolutions of the driveshaft. Just wondering where the ratio comes from, because I read that the angle drive is 1:1 (or 1:1,27)

Thanks,
Paul

Paul Wrote:

I get 1 revolution at the speedo cable for 2 revolutions of the driveshaft. Just wondering where the ratio comes from, because I read that the angle drive is 1:1 (or 1:1,27)

Hello Paul,
The 1:1 or 1:1.27 ratio is between the driven input and the output of the angle drive unit. When I get the opportunity, I'll count the teeth in the Drive gear in the gearbox and the Driven gear of the speedo drive, to determine the exact ratio. However, my mind's eye image of these two gears would make the 2:1 ratio (Drive to Driven) about right, providing that the ratio of the Angle Drive is 1:1.

Regards,

Bill

Thanks Bill,

So I checked my angle drive ratio to confirm the 2:1 factor, but I have a 1:1.27 (hand shifted, no overdrive, just another non original part I think).

I was hoping to calculate the overall ratio from wheel to speedo cable (get rid of the gear play and cable flex), but the gear ratio's are not as simple as I hoped. The somewhat odd ratio I got from the usual cardboard on the speedo cable and wheel turning, must be right then.

When I look at the overall factor and calculate back I come to a ratio of about 1:0.36 (drive to driven) ratio. It would be nice to know the actual gear ratio when you see them next time Bill. Unless of course there are many variants.

Paul

Drive worm gear has 6 teeth, speedo drive has 16. So, 1 rev of the driveshaft = 0.375 revs of speedo drive pinion.

Thanks Colin,

Now I can calculate the ratio from wheel to speedo cable instead of trying to measure it.

Paul