Max
Thanks I think (-;
Jim
Max Heim wrote:
> Oh, I guess I was thinking he had a 73 *car*.
>
> I wouldn't expect the 67 gauge face to match his other instruments, but that
> is pretty minor. If they happen to have the same "sweep", he could always
> swap faceplates, too. [But they don't -- the 78 one only reads to 85mph].
>
> I also notice Skye's page shows 80mm all the way to 1980. But even if you're
> right, it turns out that it doesn't matter.
>
> Your numbers don't look right to me. Why would a 67 and a 73 have the same
> TPM? -- they have completely different transmissions. I think if you read
> the web site closely you will see that 67 is the same as 62-66 (1040 or
> 1020), and 68 went to 1280 (but with an 80mm dial). Where the upper chart
> says Oct. 67 - Dec. 67 it is referring to the 68 *model* year.
>
> So Jim is in a situation where he has a 1280 TPM tranny and a 1000 TPM
> speedo -- the worst possible combo. But the best he can do with a 100mm dial
> is 1040 TPM -- scarcely worth the hassle. I think he needs to look into
> other solutions.
>
> I did research this to some extent a few years ago. I have a 66 non-OD car
> (1040 TPM speedo) with a Blue Label OD tranny (1000 TPM). This is close
> enough that a pinion tooth variation of 1 might make a noticeable
> difference. Also, I could easily (?) find a matching 1020 TPM speedo, to get
> even closer. Where I got bogged down was in trying to figure out the factor
> for having 175R-14 tires.
>
> on 5/21/02 9:01 PM, Larry Hoy at larryhoy@prodigy.net wrote:
>
> >> That's a different size speedo... it wouldn't fit in your dash.
> >
> > Max, Jim, Bill,
> >
> > I could be wrong but I think the 1963-1967 and the 1977-1980 cars are
> > the 4"(100mm) instruments. The 1968-76 cars are the 3 1/8" (80mm)
> > instruments.
> >
> > His OD transmission is from a 1973 car that was originally matched with
> > a 1280 tpm 80mm speedo. His car was originally built with a 100mm
> > 1000tpm speedo. According to Skye's web site the 1967 cars were
> > equipped with a 1280tpm 100mm speedo. Soooo the 1967 1280tpm 100mm
> > ought to fit in his dash and solve the problem.
> >
> > Consider that his car goes 60mph and registers 80mph a ratio of 1.33
> > (80/60). The speedo ratio would be 1280/1000 which is 1.28; almost
> > identical. After the change the 60mph car should register around 62mph.
> > I bet if Jim REALLY knew how fast he is going when his present speedo is
> > registering 80 mph he'd find he is going 62.5 mph which is what the 1280
> > tpm speedo would register.
> >
> > There is the one 'gotcha', I'm not convinced that Skye's charts are
> > accurate. In fact he has two charts on his site that seem to be in
> > conflict. (By the way this is why I've copied Bill Dudley with this
> > message, his 1967 MGB is a one owner car. Bill, would you check your
> > speedo and see if it is a 1280 tpm 4" speedo?). I suppose that will be
> > sorted out when we here from Bill, who I think is out of town right now.
> >
> > Max the 21 vs. 22 tooth gears wouldn't be able to make enough difference
> > to even justify the change. The gear INSIDE the transmission that
> > drives the pinion changed over the years, that is another solution.
> > However it requires the removal of the engine, transmission, and then
> > the swapping of the internal speedo drive gear.
> >
> > On other solution. Any COMPETENT speedometer shop can make a
> > transmission to change the ratio.
> >
> > OK now one last suggestion, then I'll quit. VDO makes a 4" gauge that
> > is programmable.
> >
> > Larry Hoy
> >
> >
>
> --
>
> ===========================
> Max Heim
> mvheim@studiolimage.com
> ___________________________
> Studio L'Image/West Coast
> 510 666 9799
> ___________________________
> Studio L'Image/East Coast
> 212 242 3366
> ___________________________
> www.studiolimage.com
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