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GT6 mk3 Speedometer

Stewart Vacher

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Not sure that this is the right place to post this question but could not see it fitting in the other headings so here goes:


When taking part in last weekends New Forest run my speedometer started intermittently to make some awful whirring noises. It sounded like a worn out food mixer. The mileometer and tripometer stopped incrementing during the noisy periods.  It didn't get any better when I tried to investigate and the front rim and glass fell out  :o. This only increased the decibels to a headache inducing level. All the time the noise was going on the needle was going mad spinning around and around until it finally flew off!!!


As a result I am now scouring the internet for a replacement, which brings me to my question.


All the speedometers I can find quote what appears to be serial numbers similar to those on the front of the dial on mine but not exactly the same. Does anyone know what the significance of these numbers is?


Mine reads :-

                        SN-6203/42A                  1152


Most of the speedometer I have found quote SN-6203 but the other numbers vary.

As these appear to be quite expensive items I obviously don't want to end up with the wrong one.


Also does anyone have any advice where I might get a good reasonably priced replacement?


Any help would be greatly appreciated.



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Have a look at this




The 42A may be to do with the calibration talked about. The calibration depends on the diff ratio, the gearbox, size of tyres etc. You are wise not to jump for a different number, wait for one to come up or having read the above, repair it! :lol:

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if you cant strip and repair diy fashion 


then other idea's are 








http://www.caigauge.com/automotive      who make smiths instruments and can do repairs themselves or via   speedy /\ and others   



see my notes on Gully.s  speedo problems     http://forum.tssc.org.uk/index.php?/topic/1401-gt6-speedo-noise/



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Thank you guys, I knew I could count on someone on the Forum to give me some good advice.

Now I am a lot wiser on the relevance of the code numbers, and reading the repair article have a better handle on how it works.


I removed the speedo last night and had a good look at the mechanism. It appears to me that there is so much play in the spindle that the magnetic wheel is scrapping  the drag cup, which is causing the problem. Although normally I would have a go at fixing most things on this occasion I think I will leave it to the experts to fix and calibrate as I might end up 'Fixing it so nobody else can'. To that end I have asked speedycables to give me an estimate to refurbish.

If that comes out to be too costly I will again try to search out a secondhand one, this time knowing a little more what serial number to look for.



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Hi Gully,


I was lucky as far as getting it out in that I found it only had one of the two original clamping nuts in place. This makes me think a previous owner must have removed the speedo sometime in the past and maybe because it was so difficult to fit didn't refit it. I think I might have to remove the centre dash panel when I replace it as I want to fix it properly.

The one that was fitted was nearest the steering column and just about accessible from underneath once I had disconnected the footwell heater supply hose.

Yes I think that I might be wise to have a plaster or two ready as Pete suggests when I get that far!



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It's easy enough once you remove the central console and know what the fixings look like. Do you have a voltage regulator strapped to the back of the speedo? I would take the opportunity to replace it with an electronic one that doesn't need to earth on the speedo.

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