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Help needed vs v8 conveted to 6 speed-now speedo won't work

amanda

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Hi everyone.
I have just bought a vs v8 sedan with a 6 speed box out of a vt ss.The guy i got it from said when it was converted to 6 speed the speedo stopped working.Any ideas on how to fix it would be great.
 

amanda

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Nah was originally a v6 auto berlina then it got converted to v8 auto then the auto was converted to 6 speed manual
 

The1

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do you know what's been changed? has it got a manual ecu? Was the wiring changed over?
 

amanda

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My brother who is a qualified mechanic had a quick look at it and he seems to think it still has the auto computer in it as it idles high and thinks it may also have the v6 dash still as it revs to 7000 in 4th and 5th gear
 

amanda

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i don't think its an LS1.all i could tell you is it has 185 on the top of the motor(but these can be changed can't they?)engine number starts with vu.
What other info could i give you?I only got the car yesterday
 

Cheap6

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"185" indicates it's a 5.0l i.e. not LS1 so that's a start.

The tach can be fixed. There's a how to on that on here - it requires moving a resistor and a wire link on the instrument cluster circuit board.

Your brother should be able to find terminal C12 at the PCM (engine control computer). That's the speed signal from the PCM to the instruments. With that backprobed (your brother will know what that means) to earth, you should be able to see a frequency output (measured with a digital multimeter) when the car is driven. If not, the PCM is probably not getting a speed signal and you will have to go to the trans. end. If there is a signal, the fault is in the cluster.

Most likely it will be at the trans. end. Again at the PCM, there should be a frequency signal across terminals F5 and F6 (when backprobed) when the car is driven. If not, either the sensor is not connected to the PCM or the sensor is not working.

Even with the sensor working, the speedo may be inaccurate as I'm not sure that the VT manual 6-speed speed sensor output matches a VS auto. PCM (it might). If not you can use one of the Jaycar speedo corrector kits between the sensor and PCM or have the memcal ("chip") in the VS PCM rewritten to suit.
 
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