Anthony Rhodes wrote :
> I had meant, I thought the TR6 speedos were
> always 1000
> with the J-type. I was not positive if they had differing drive gears for
> the A-types or not. On the earlier cars with the A-types, the drive ratio
> was always the same (10:15, I think).
I think of it as 1.5:1 (output shaft turns 1.5 revolutions for every
revolution of the speedo cable), but otherwise that's right.
> At least on the A-type, I thought the speedo
> drive gear was
> able to be removed from the outside (MUST be removed from the outside) in
> order to dismantle the OD.
Also true of the J-type, again we're just talking semantics here.
> Also, on the A-type, there is a scroll (10
> lands, I think) on the OD output shaft to turn the speedo drive gear, and
> this is not able to be altered (at least without exchanging the entire
> part). I presume that there were different OD drive gears than the
> "standard", whatever that was (15 teeth, I think).
To the best of my knowledge, all A-types (even those for other cars) had the
same number of teeth machined into the output shaft (annulus).
> Were there different speedo drive gears ("driven gear", as you
> more properly
> called it), or were they always the same?
There were definitely different driven gears available, but I don't know
whether different ones were used on the TR6 or not.
> I'd have thought it would be
> easier to change these plastic doodads from the outside and keep the same
> scroll on the "drive gear".
If you are British Leyland building a car, you simply assemble with the
proper parts to begin with and it doesn't matter how hard they are to
change.
> (it would also allow a slightly finer ability
> to alter the ratio. I presume that since the adjustment is SO coarse when
> altering only ONE of the gears that they BOTH must have been able to be
> altered....
That is true on the J-type, and is where the problem arises. The J-type was
used in quite a few different cars, including Triumph sedans, Volvos, and
even MGB. For every application, there is a different pair of drive and
driven gears. Unfortunately, many people selling J-type overdrives to
unknowledgeable Triumph owners neglect to mention this detail. I once
contacted one of the more common sellers on eBay ... when I told him that
the unit he was selling as a "TR6 overdrive" most likely had the wrong
speedo drive gear (and that the unit had to be disassembled to change it),
his response was "I know".
Rimmer Bros also once sold a "reconditioned" overdrive to a friend of mine,
that turned out to have the wrong gear inside it. They eventually made it
right, but it took a long time to resolve the problem.
Randall
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