Astra/ corsa b speedo

[ukhozi]

I have a Astra GTE speedo and tried using an aftermarket sender for speedo but can't get anything near the correct speed.
Does the sensor output have to go via a ECU?
I was hoping it was analog like the MG Maestro one I had before which was 8 pulses per rev. Is there an aftermarket transponder that works at wheel speed as I need to take it from the front wheel, no gearbox take off point. 740 revs per mile.


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[ukhozi]

Also, anyone know what the little red slide switch on top of the speedo is for?

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[coupe77]

You need the gte transponder as the dash takes the pulse from that
It has 3 wires
You might have to fit the early cable box
Or find out what the wires on the corsa transponder do then work out the pulse wire to the speedo
Other hub speed sensors take the pulse from the abs ecu


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[ukhozi]

No GM gearbox to fit transponder to. It will have to be front wheel driven.
Apparently the switch gives a change of 2.56:1 ratio difference for the same pulses.

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[ukhozi]

Still slogging on, I now know the transponder for the speedo takes its pulses from a gear in the gearbox, as it counts the number of teeth. so what gear is it or is it a sensor ring and how many teeth so I can then fit the corrected number of teeth to my front hub LIKE an ABS ring.

[ukhozi]

Still no answer.

How many pulses are needed to get the GTe speedo to read 60mph?

How I get those pulses will be down to me but I still need an answer.

I have been told that I should be looking at 15,000 ppm
÷ by 750 wheel revs pm that gives 20 pulses per wheel rev.

Help!