Sierra 2.0 Ohc

[Guest jcowing]

Hello,

 

I am in the latter stages of building an S7, and have hit a barrier. I need to find to what the drive shaft ratios are for a Sierra 2.0 OHC, so that I calibrate my speedo. I have looked in the manual with no luck, unfortunately I have no access to the original donor car where I am told this information will be avaliable.

 

Can anyone help me with my dilema.

 

Thanks,

 

James..

[Guest Ant]

Depends what you mean by "drive shaft ratios". For speedo calibration there is the following factors:

 

- Tyre diameter

- Differential ratio

- Speedo drive ratio

 

The diff ratio is probably 3.92 but depends on which model of donor you had. See haynes for the full list. The speedo drive is common for all type 9 gearboxes - not sure what it is, but most gearbox places or speedo servicing places will know. The tyres are up to you.

 

The best way to to count the turns of the speedo cable over a measured distance - say 20 turns of the wheels. That way you take all three factors together and don't need to worry about them individually.

 

Ant

[Guest jcowing]

Ant,

 

Thanks for your reply, not sure why I said drive shaft ration, I meant to say diff ratio. I am trying to calibrate an electronic speedo. I have found out that I need the circumference of the wheel, but need to do some calculations involving the diff ratio of a 1982 Sierra 2.0 OHC. Do you think the diff ratio that you said on the last post will be the one that I need?

 

Thanks for your help,

 

James..

[Guest stevie b]

ETB instruments give advice on their web site on how to claibrate speedos using an empirical approach they call it the cardboard disc method.

 

Its at http://www.etbinstruments.com/homepage.htm

 

Hope it helps

 

Steve

[Guest Ant]

If it's an electronic speedo then the card method is not needed as the speedo cable isn't used.

 

Regarding the diff ratio I'm not sure if the 3.92 ratio is correct for your donor. Your best bet is to have a look at the haynes manual and see which one looks right for the car you had. Failing that someone else on here may know.

 

Ant

[Guest boggie]

IIRC All sierras had a 3.62:1 ratio, with the exception of:-

 

1.6 estate (except 'economy' version)

2.0 injection (eg 2.0is and 2.0 4x4)

 

these had a 3.92:1 ratio

Hope this helps,

Boggie.