"Mike Kitchener" wrote :
>
> The main advantage that I can see is if you need to down-change
> quickly when running in overdrive then the overdrive will cut out and
> stay out .
> Also it would be possible to use all seven gears easily from a
> standing start to overdrive top.....could be fun but superfluous ?
> All comments welcome .
I've not tried the 'logic device' sold by Revington, but I've considered
building something similar. The main advantage (to me) would be that I
occasionally forget to disengage the OD when stopping, and the logic
device would do it for me. Otherwise, it seems fairly useless, as I
only use 2nd OD when I'm trying to squeeze the last ounce of performance
out of my (rather tired) engine, and 3rd OD is so close to 4th direct
that IMO it's useless anywhere but on a 3rd gear road course (where
otherwise you would have to declutch and take your hand off the wheel to
shift back and forth between 3rd and 4th).
Moving the control to the top of the shift knob might be an advantage,
but I find the TR3's OD control to be very easy to use, with both hands
still on the wheel (which can be important).
"J.H. Roulleaux" wrote:
> I heard from people
> stopping with 2nd gear engaged in overdrive and than reversing,not
> good for an overdrive.For that reason I did not mount the 2nd gear
> switch .Understanding that the overdrive pump is operated by the
> propshaft I don't see how it could disengage with the propshaft not
> rotating,but can understand that it will disengage as soon as you
> back up and the pump is resuming pressure. Is that soon enough
> to avoid damage.
The hydraulic pressure holds the OD clutch in the engaged position. If
pressure is lost, either because of leak-down or because the solenoid is
released, there are springs that force the clutch into the direct drive
position. For this reason, it can be dis-engaged at any time, the prop
shaft does not have to be rotating. The A-type can also engage at any
time, as it has an accumulator that holds pressure, but the J-type does
not.
So, assuming the controls work correctly, there is no problem with
stopping with the switch in the engaged position, then reversing. As
soon as the gear selector is moved to neutral in the process of shifting
to reverse, the OD will disengage, and it does so very quickly.
Randall
59 TR3A daily driver TS39781LO
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