Larry,
Thanks for the info. I'll wait for your final analysis.
Jim
Larry Hoy 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
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