Hello,
This got discussed once before but never properly resolved:

If I fit an XB12 tacho on an XB9, will it read correctly?

I have a vague impression that Maz said it would, but maybe I imagined it?

Thanks!

Spudley had a 9 speedo on a 12 and it read "fast"

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08 Specialized Langster

Thanks Pash. But what I am really looking for is the non-anecdotal answer based on technical specifics (ie 'yes' or 'no' because it is driven off ABC).

And for a 12 tacho on a 9...

Maz???

My XB9 and XB12 service manual quote same frequencies for the same speed, so I would not expect any problem with swapped speedos.

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"It is often said that before you die your life passes before your eyes. It is in fact true. It's called living."
Terry Pratchett

Assuming that you mean the speedo, they are NOT interchangeable between the 9 and 12.

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Mithered ta death.
92 MB
96 S2T
98 S1W
00 M2
01 X1
03 P3
10 CR

Is this with the new gearboxes only?

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"It is often said that before you die your life passes before your eyes. It is in fact true. It's called living."
Terry Pratchett

Sorry, yes, I mean the speedo.

I have a Uly speedo fitted to my 06 City X at the moment and the revs certainly seem to be correct but it is more difficult to tell whether the indicated speed is correct.

One theory I heard was that the revs are correct because that comes from the ignition (?) and the speed should be OK because it is read from the final drive which is 1:1 on both XB12 and XB9.

I think the speedos work differently on the 08+ models but this wouldn't affect me.

The tacho signal comes from the ECM and the speed signal from the sensor above the 5th gear wheel.

For 2003 - 2005 models the service manual says 100 kph = 1443 pulses (42 teeth) regardless if XB9 or XB12. For a 2007 XB12X the service manuals says 100kph = 1650 pulses, but I don't have no number for XB9 to compare with. IIRC in 2006 the new gearboxes were introduced, so this might be the year since when the speedos couldn't be swapped anymore.

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"It is often said that before you die your life passes before your eyes. It is in fact true. It's called living."
Terry Pratchett

Thanks Gunter. I know that 2006 was indeed the year of the new gearbox for the XB9SX. If new the gear boxes were also fitted to the XB12s (I don't know) then wouldn't the speedos remain compatible? ie same pulses for each?

I can only reiterate the Spudley problem, which was an '07 XB12 engine in an '03 XB9. The '03 XB9 speedo over-read with the '07 XB 12 engine (160-ish when mine was reading 140-ish). This may or may not help you.

Bungle, I think the answer to that is in Gunter's response:
The 07 engine is giving out 1650 pulses at 100kph, whilst the 03 speedo thinks that 1443 pulses is already 100kph, so it over reads. It looks like the problem is due to the different model years and not XB9 vs XB12. An 07 XB9 engine would also have over read in this case.

My kph speedo is from an 07 Uly and it does SEEM to read OK for my 06 City but I will try to go out over the weekend with a mate and confirm it one way or another.

I think the way the speedos are controlled may have changed again with the 08 models. In which case, this would suggest:
speedos from 03-05 compatible regardless 9 or 12 - based on Gunter's info;
speedos from 06-07 compatible regardless 9 or 12 - to be confirmed by my tests;
speedos from 08 ... who knows?