Ed, the speedo gearing is done via a mgnetic device. So in fact, the
different gearing is reached via different magnetic forces applied.
There may also be a different gearing, but if this is unobtainable for
any reasons, you may calibrate the speedo to your requirements.
Gernot
> ----------
> From: Ed Woods[SMTP:fogbros@nb.net]
> Reply To: Ed Woods
> Sent: Wednesday, May 06, 1998 1:06 PM
> To: Triumph Mailinglist; fred thomas
> Subject: Re: TR4 Speedometer
>
>
> Fred and all,
>
> Maybe I didn't make myself clear. I know that "speed is speed", but
> the fact
> remains that there is a significant speedo error after installing o/d.
> It appears to me that the only thing that can cause this is a
> difference in
> gearing to the speedo. I cannot find any parts book that indicates the
> o/d
> speedo drive gear is different from the non o/d speedo drive gear. In
> fact,
> other than the materials used to fabricate them, all TR speedo drive
> gears
> that I have lying around have the same number of teeth. And, yes, it's
> o.k.
> to make adjustments to road speed in order to stay out of the hands of
> the
> law, but what about odometer accuracy, as in rallying? There's enough
> to do
> on a rallye without having to constantly adjust the odometer mileage
> in
> anticipation of the next turn instruction.
>
> So, my question remains: is any lister aware of a different speedo
> gear
> ratio for o/d cars?
>
> Ed Woods
>
> P.S. We fitted the "A" type overdrive to the 76 TR6 gearbox using a
> new
> mainshaft purchased from TRF that allowed us to use all the original
> steel
> bushing internals. Why Triumph made this mainshaft for gearboxes that
> used
> the "J" type, I don't know; but it was a nice option since I'm partial
> to
> "A" types.
> -----Original Message-----
> From: fred thomas <vafred@erols.com>
> To: Ed Woods <fogbros@nb.net>
> Date: Tuesday, May 05, 1998 10:59 PM
> Subject: Re: TR4 Speedometer
>
>
> >Ed Woods wrote:
> >>
> >> Ed,
> >>
> >> Why would an OD speedo be different from a non OD speedo unless the
> diff
> >> ratio was also different? I'm curious because I've fitted an OD to
> my
> >> brother's TR6 and cannot understand why the speedo is 20%
> optimistic.
> >>
> >> Ed Woods
> >> -----Original Message-----
> >> From: Edward R. Purcell <epurcel@bellsouth.net>
> >> To: triumphs@autox.team.net <triumphs@autox.team.net>
> >> Date: Tuesday, May 05, 1998 5:01 PM
> >> Subject: TR4 Speedometer
> >>
> >> >
> >> >My TR4 speedometer has never worked, so a good used one is on my
> >> >shopping list for Carlisle this weekend. Mine shows 1184 for the
> turns
> >> >per mile number on the face. Is this the correct speedometer for
> a 1964
> >> >non-overdrive TR4?. Many thanks for any info on this matter.
> >> >
> >> >Thanks Again, Ed Purcell
> >
> >Speed is speed is speed, the only difference is the gear coming out
> of
> >the trnny, how many teeth. O/D has no effect on your speed at all,
> just
> >RPM. The speedo is geared to the trans. not the rear end.
> >
>
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