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.
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