On Tue, 27 Mar 2007 07:29:31 -0400, "Nosey"
<kfrei43@[EMAIL PROTECTED]
> wrote:
>Willis wrote:
>> He also put potential blame on the fact that my car has a stall
>> converter. He said stall converters were worthless unless you were
>> heading to the track. Does he have a point or is he just a way-too-
>> opinionated transmission tech?
>
>
>You can run into transmission problems if your cruise rpm is below the
>converter stall speed. If the converter is slipping all the time it will
>create extra heat. Heat is not friendly to automatic transmissions.
Many people do not like higher stall converters, but they
have their place. I know that Ford has used converters as
high as 3000 as I have one in my 351CJ Torino. Please note
that it is very im****tant to have the stall matched to the
engine, drive trani and vehicle weight instead of just
picking it out of thin air for best driveability and
performance. Go too high on the stall and it is miserable
to drive on the street as well as a waste of power and fuel.
Go too low and it is a slug and may not idle in gear. Stall
speed higher than about 70% of the engines peak torque RPM
and you are not helping yourself overall as this can result
in high fluid temps especially if you have a tall rear gear
or large diameter tires adding to the cruise load. If you
are runnig it 1/4 mile at a time, you need to be more
aggressive in stall speed. If you are always on the street,
stay conservative but, give it enough higher stall to idle
with your cam. If you are on the street, you also need to
be cautious of over camming or you can make the ride
miserable.
Vehicle speed has nothing to do with a C6 converter rated
stall speed. The stall speed you see advertised or rated is
usually either the flash or static stall speed with the
vehicle not moving with a particular engine. A more
powerful engine will stall at a higher RPM with a given
converter. That is one of the measures we would use in
determining whether an industrial Diesel engine was
producing its rated output. In any case, low speeds are
easier on a non-locking converter than higher speeds. The
higher the vehicle speed, the more a non-locking converter
will normally "slip". A higher stall speed converter just
"slips" more normally and will have a higher percentage of
"slip" as the vehicle speed increases which will result in
increased fluid temperatures. This is true of any
non-locking converter. That is why it is recommended to use
the biggest cooler you can fit when a higher stall converter
is installed.
As far as the OP's problem goes, I would assume the trans
has a modulator valve unless it has has a full manual
conversion installed. I would make sure the vacuum line
from the intake to the modulator located on the right front
side of the C6 is intact and in good condition with no
indication of material swelling or collapse of the rubber
connector hoses as may occur over time. Pull the hose to
see if it has any indication of fluid in the hose. If fluid
is found, the modulator is leaking. The modulator controls
the 1-2 ****ft points based on engine vacuum - nothing else.
his has the effect of sensing engine load. If the engine
has a problem or needs tuning to operate at correct vacuum
lavels, that will need to be addressed before going any
further with transmission troubleshooting. Once it can be
determined that the engine is delivering good vacuum to the
modulator, a quick check can be done by acelerating the car
with mimimal throttle. It should up****ft 1-2 between 8-12
mph depending on the power train setup. The service manual
will have a method of checking modulator operation with
pressure guages. In any case, if it is not doing this and
the transmission did at one time operate properly, I would
replace the modulator with a new adjustable one. This is an
easy repair with minimal loss of fluid and can be done by a
novice. Just make sure the push rod is not lost and is
replaced with the modulator. The modulator should be
adjusted either for proper pressure or up****ft speeds
depending on what is available to work with. The OP would
do well to order an ATSG manual for the C6 which will
contain all the info that should be needed. They can
usually be found or ordered at NAPA stores and any trans
supplier worth going to. They may also be available on
Amazon.
If replacement and adjustment of the modulator and connector
hoses does not do the job, I would next remove the tailshaft
housing and remove the road speed governor to free it up as
a stuck RS governor may cause the indicated problems. I
suggest the modulator first because it is easier to do first
and less invasive of the trans.
If the trans has not been recently serviced, this would be a
good time. Make sure the converter is drained as well as
the pan. Make sure the filter seal is properly installed
and that there is only one in there. More seals in the hole
are not better!
Good luck
Lugnut
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