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Hi again to all.

I am desperate for so info.

I have original ek speedo on the dash, run a Th400 gear box and shortened HZ Large salsbury dif with 3.36 crown wheel.

The speedo at this stage is reading to fast, at about 50 to 60 Ks speedo reads 50 mile and hour ( 80 k ).

The plastic gear in the box is brown with 37 teeth. I am advised to fit a bigger gear ( one with more teeth, a light blue gear has 45 teeth )

does anyone have experience in relation to this.

I am still trying to get it passed by the engineer and he said he has to do a speedo calibration and it has to be within 10 % of correct speed.

Any info appreciated.

Luke

No idea sorry I used a castlemain rodshop cable turbo 350 to original dash.

That one's got me puzzled.I've run it around inside the 'noggin and if you've gone from 3.89 to 3.36 the engine revs would have to decrease for the same set about of speed.

For example:- 3.89 at 60 mph might be ,say 3500 rpm

3.36 at 60 mph might be ,say 3000 rpm.

So your speedo should be running slower than actual speed, not faster than actual speed

There again, you have changed the box as well and maybe the speedo gear is contributing a lot more to the indicated speed problem than would appear.

I did have some info on the various speedo gear colours needed for diff ratio changes but can't find it at present.

Anyway, if this helps,

From my calculations ( late at night ) you will need to speed the driven gear ( the plastic gear ) up when going from a 3.89 to a 3.36 actually because you engine revs diminish for the same speed therefore your speedo will also indicate a slower speed than actual speed..... does this make sense??

You would need a smaller driven gear ( the plastic one ) to achieve this.

My late at night, I'm very tired calculations work out that you need to increase the driven gear speed ( the plastic gear ) by 16 % which is the percentage difference between 3.36 and 3.89.

I hope this is a bit of help,..... and is right

Terry.