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.
>
> --
> Athol
> <http://cust.idl.com.au/athol>
Linux Registered User # 254000
> I'm a Libran Engineer. I don't argue, I discuss.
|
