instrument cluster question

Hi gang. Back in 2000 I bought a Focus here in Ontario. The little darling never read Consumer Reports so it's been my most enjoyable automotive ownership experience in over 40 years. I was going to trade it this year but
it's running so well that I decided to keep it until it needs major repairs.
But I missed having a tachometer (it's a manual) so I located a cluster from a ZTS from a recycle yard over the Internet. It arrived by Purelator and I put it in. It works but the tach and speedo didn't seem to correlate too well. I brought up the digital readings on the odometer to check it.
The digital readings seem fairly accurate based on highway markers and published road test gearings. So using them as a basis I get the following:
a) the speedo is about 2.5kph (1.5mph) high until about 100 kph, then drops to an error of 1 kph high at 120kph.
b) the tach is about 150rpm low from 1300 to 2200, then drops to very little error by 3500. And strangely enough it's dead accurate at idle.
Looking at my factory service manual, it warns that a replacement cluster should always be shipped in the correct position, otherwise "silicon fluid can leak out and cause inaccuracy". They don't say what that shipping position is, but I presume it is the same as when mounted in the dash.
When I opened the box it was lying on its back, so this might be the problem.
Does anyone have experience with this? It is likely to correct itself with time? I couldn't see any adjustments on the tach, but aftermarket tachs have adjustment screws, so is there any way to adjust out errors?
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The speedometer error is about what I would expect. The 150 rpm max tach error is a little more than I would hope for, but again, it's not so far off that it would indicate a problem with the gauge.
I doubt the shipping position had anything to do with it, and I would accept it.
I am pretty sure that there will be no mechanical adjustment on either the speedometer or the tachometer. As part of the diagnostics that happen when you put the trip meter into its diagnostic mode, you should have noticed all the needles (speedometer, tach, fuel gauge) sweeping to full range. This is a clue that those needles are driven by stepper motors (digital) rather than being analog (D'Arsonval) movements.
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Appreciate the useful comments.
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Hi Mark,

Are you sure these are driven by steppers? In that case, why do the needles park when you remove power from the cluster? Why do they show inertia at both ends of their travel? Why do they not make noise while in motion?
My understanding was that these types of dash indicators (analog needles in front of an all-digital back-end) are regular analog voltmeters (current meters, really), driven via PWM. In which case there probably _would_ be a zero point adjustment screw, possibly sealed inside the body, but it would shift the whole scale - so I still wouldn't advise tampering with it :)
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