speedo drive gears for Ford 4-speed ?

[KayTee]

Hi, all !

 

Hmm, I've got a Quaife/FlowTech 4-speed box, an RS2000 axle with 3.54 cwp, and A032Rs in 185/60-13.

 

Is there a speedo drive gear set available for that gearbox that would allow me to calibrate the whole caboodle for a Smith's speedo ?

 

Thanks & Cheers - Karsten

 

[deanteam]

The Weale book gives a table on page 223 with the alternatives.If you don't have the book do you have a fax number? However I suspect that your tyres may have a smaller circumference than that used for the tables, slower than indicated? I think you can have the speedo modified but you need to know the distance that car goes per revolution of the speedo cable drive.

[KayTee]

Thanks !! *Whoops!* I have the book ... should've looked before I shout ...

 

I have the accurate cuircumfence of the tyres (DT catalogue listed them - 1683 mm).

3.54 rear diff suggests ... 0,47542373 m/prop-shaft revolution

 

Eeh ... that gets me where ??

 

puzzled - Karsten

[KayTee]

Hmm ! A bit of basic maths later ...

1,683 m circumfence, that's 956,030897 wheel revolutions per mile, considering 3.54 diff, that means 3384,34938 prop shaft revolutions per mile. Correct so far ?

Now, the speedo is calibrated for 1000 revs per mile, right ? That gives me a relation of 0,2954777 (how appropriate!). The Wheale book seems to say that the gearboxes drive gear is always 7 teeth. To get down to that relation, I'd therefore need 23,6904456 teth on the driven gear. I'd go with 24 teeth.

 

Does all that seem plausible, despite 24 teeth being intended for 3,89 and 3,92 diffs ??

 

Thanks & Cheers - Karsten

 

PS.: With a 24 teeth driven gear, do I calculate correctly that this gives me an error of 1,3 % ??

 

Edited by - KayTee on 12 Mar 2001 10:22:45

[deanteam]

I am not a mathematical wizard but I think you are right.