"Stevo" <stevekelepouris@[EMAIL PROTECTED]
> wrote in message
news:hBoKj.6850$n8.5995@[EMAIL PROTECTED]
> Thanks Mark and Athol for your info.
>
> This has helped me sort out a problem I've been having and wondering
about.
>
> My modulator was stuffed so I installed a new one (with the adjusting
screw)
> didn't make much difference.
> My VH commodore trimatic was still flaring between 1st & 2nd and
slipping
in
> 3rd.
>
> After reading this post I thought I would do a bit of "trial and error"
(had
> nothing to lose) - I ended up making quite a few turns clockwise and
fluked
> it because now it changes nicely into third and doesn't slip anymore -
> Fantastic! (kickdown works better too)
>
> Still flares between 1st & 2nd though, but I can get by with starting in
2nd
> and ****fting up to drive.
>
> Steve.
> (I tried dropping the fluid and adjusting the band, didn't make much of
a
> difference, but I noticed that now when I start in 2nd the change
between
> 1st & 2nd is more harsher or abrupt).
>
> "Athol" <athol_SPIT_SPAM@[EMAIL PROTECTED]
> wrote in message
> news:1206776248.35399@[EMAIL PROTECTED]
> > Mark Kelep <mxarvkkezlly2@[EMAIL PROTECTED]
> wrote:
> >
> >> Apparently modulators on early auto tranmissions (trimatic for
example)
> >> had
> >> an adjustable screw just where the rubber hose bit goes on.
> >
> > I think that you'll find that the adjustable modulators are an
aftermarket
> > tuning item. I don't know if any auto had an adjustable modulator
> > standard.
> >
> >> What is its exact purpose and is it really adjustable?
> >
> > The purpose is to allow adjustment of the amount of vacuum required to
> > cause
> > the gearbox to do all the things that depend on vacuum. The main ones
are
> > up****fts and down****fts at mid-throttle and load. Generally, there
would
> > be
> > something else (linkage, cable or electric switch and solenoid)
connected
> > to
> > the throttle to control full throttle down****fts (ie kickdown). From
> > experience, the relatively small amount of adjustment available can
make
a
> > huge difference to the ****ft point. Get it wrong and it'll be an
absolute
> > PITA, either not changing up or not kicking back soon enough...
> >
> > Where there is an electric solenoid for kickdown, it's also normal for
the
> > amount of vacuum to be used to control how much clamping pressure is
> > applied
> > to the clutch packs in the gearbox. An adjustable modulator affects
this
> > as
> > a coincidental side effect - the adjustment doesn't really have enough
> > range
> > to affect it much. IIRC, some gearboxes with mechanical linkages
still
> > have
> > some pressure control from the modulator.
IMHO, with cars that have old and worn automatics, you can get the most
out
of them before the dreaded rebuild or swap with a lucky-dip trans from a
wrecker by getting to know what speed, gear selection, throttle setting
etc,
that gives smoothest and therefore lowest wear operation, to get those
last
kilometers outa her.
My old and worn LTD auto has selectomatic which allows you to take -off in
2nd gear. This eliminates one change, which the 351engine handles OK.
When
its time to slip into Drive,.I always do it with my foot off the throttle
for that small period of time which allows me the op****tunity before it
does
the change itself. This is one of the advantages of having an oil-pump
which
is a bit slow in increasing oil-pressure to execute the change This extra
time means you aren't allowing the trans to change under high torque,
which
causes accelerated wear of what friction material is left on the bands and
clutches.
Jason
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