Question for the Tranny experts

H

heinz wittenbecher

New member
Mar 1, 1998
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Hi folks.

I'm trying to determine tranny fluid flow in an effort to improve cooling at
low speeds.

Is the reason for increased pan temperature in stop and go traffic because
of no cooling air flow or because not enough tranny fluid is being
circulated through the cooler?

I'd like to think it's because of insufficient air passing over the cooler
fins as that's an easy fix (add a fan) but thought I'd ask first.

Another question is whether coolers such as the Perma-Cool actually have a
thermostatic control in them so as to allow fluid to get up to normal temps
or are they always in full cooling mode?

I currently use a passive external cooler without any fluid passing through
the radiator. The reason being that it was thought that it could not be
sufficiently flushed to assure all metal would be gone from prior tranny
failure.

TIA for your comments

Heinz
 
>Is the reason for increased pan temperature in stop and go traffic
>because
>of no cooling air flow or because not enough tranny fluid is being
>circulated through the cooler?
>
Certainly, reduced air flow has to be a major factor but how about the
impact on moving parts by stop and go traffic?

David Lee Greenberg
GMC Motorhome Registry
200 Macfarlane Drive PH 4
Delray Beach, FL 33483-6829
800-827-9989
 
> Is the reason for increased pan temperature in stop and go traffic because
> of no cooling air flow or because not enough tranny fluid is being
> circulated through the cooler?

Hienz, I don't nearly qualify as a "tranny" expert, but I know that the two
reasons you mention both have a negative effect upon cooling, and that the
reason for most of the increase in temperature comes from the extra heat
that is generated whenever the transmission is "slipping." This occurs when
idling at a stop, and especially during starts, when the torque converter is
slipping to multiply the torque to the drive wheels. The best thing to do
when you have high transmission temperatures is to go easy on the throttle.

Scott Shean
78 Royale
Baton Rouge, LA
 
>
>
> > Is the reason for increased pan temperature in stop and go traffic
because
> > of no cooling air flow or because not enough tranny fluid is being
> > circulated through the cooler?
>
> Hienz, I don't nearly qualify as a "tranny" expert, but I know that the
two
> reasons you mention both have a negative effect upon cooling, and that the
> reason for most of the increase in temperature comes from the extra heat
> that is generated whenever the transmission is "slipping." This occurs
when
> idling at a stop, and especially during starts, when the torque converter
is
> slipping to multiply the torque to the drive wheels. The best thing to do
> when you have high transmission temperatures is to go easy on the
throttle.
>
> Scott Shean

I'll buy that Scott, but while the tranny is "slipping" is there still lots
of fluid circulated through the cooler? is there a route back to the pan
that doesn't go through the cooler, I.e. is only a portion of the tranny
fluid being passed through the cooler?

Sorry about the dumb questions (oops there arn't any dumb questions), but
the tranny just seems like a magic black box to me that I'd like to figure
out some so that I can help "it" to take care of my "me" and my GMC.

If there is indeed only a portion of the fluid going through the cooler than
the Ragusa Pan has much more value than originally thought.

Heinz
 
>
> I'll buy that Scott, but while the tranny is "slipping" is there
> still lots
> of fluid circulated through the cooler? is there a route back to the pan
> that doesn't go through the cooler, I.e. is only a portion of the tranny
> fluid being passed through the cooler?
>
> Sorry about the dumb questions (oops there aren't any dumb questions), but
> the tranny just seems like a magic black box to me that I'd like to figure
> out some so that I can help "it" to take care of my "me" and my GMC.
>
> If there is indeed only a portion of the fluid going through the
> cooler than
> the Ragusa Pan has much more value than originally thought.
>
> Heinz
>
Hienz, I have looked at the manual, but it is not clear to me exactly how
the oil flow to the cooler is controlled. The oil pump runs at engine speed
and the oil flows though the pressure regulator and the vacuum modulator.
The oil then flows to the converter, the cooler, the transmission, the pan,
the filter and then back to the pump. This is where we are going to need a
"tranny" expert to tell us how the pressure regulator and the modulator
effect the oil flow to the converter (relative to vehicle speed/engine speed
etc.) and whether all or part of the converter flow goes to the cooler.

Thanks to you, I now know more than I ever did about the internals of the
transmission, and I still know almost nothing. Hopefully, someone will come
along and help us out.

Scott Shean
78 Royale
Baton Rouge, LA
 
I COULD crash around through the Owner's Manual, but being the lazy sort
wondered if one of the tranny experts in here could tell us all about the
fluid flow rates through the tranny at various engine RPM levels. Are they
linear? If they are linear, the Ragusa pan is starting to look like part of
the solution on the basis that if the fluid isn't moving through the aux
cooler during those stop and go, temp build-up situations, the cooler will
not have a chance to do its intended job.
Anybody want to do a little "Showboating" on this important topic? :-)
Dick 75 PB in Atlanta

>
>
>> Is the reason for increased pan temperature in stop and go traffic because
>> of no cooling air flow or because not enough tranny fluid is being
>> circulated through the cooler?
>
>Hienz, I don't nearly qualify as a "tranny" expert, but I know that the two
>reasons you mention both have a negative effect upon cooling, and that the
>reason for most of the increase in temperature comes from the extra heat
>that is generated whenever the transmission is "slipping." This occurs when
>idling at a stop, and especially during starts, when the torque converter is
>slipping to multiply the torque to the drive wheels. The best thing to do
>when you have high transmission temperatures is to go easy on the throttle.
>
>Scott Shean
>78 Royale
>Baton Rouge, LA
>
>
 
> I have been reluctant to mention these things because nobody else
> has. But if we no longer have to hold our piece then here is mine.

Arch,
If someone implied "hold your piece", forget it real fast. I for one
appreciate all the stuff you dig up :-).

My memory ain't all that good [g] but I do believe it was your digging that
excavated the AV10 for me. And if it wasn't you, my apologies and thanks to
all "diggers". (Trying to keep my butt covered :-)

Anyways... you just keep excersizing them shovel fingers and keep digging up
the neat stuff.

Heinz
 
> It was me. I was trying to find the ultimate toy for you. You did not
> like my lighted rear view mirror.
>
> Take Care
> Arch
>
>

I may not have liked the mirror [g], but I sure do like the AV10. Thanks
again.

Heinz
 
[Admin note - Clark, this post bounced as it was HTML enhanced. Please
be sure that your email program is set for "plain text" only.
Thanks! Patrick]

Just to add my $.02, one possible reason for the temp going up in stop
and go traffic is related to engine speed. The oil pump in the tranny
is driven by the engine. This is the source of oil circulation through
the external cooling system. So lower engine speeds mean less external
oil circulation. Of course the slippage in the torque converter is the
source of heat to be dissipated. At lower engine speeds and higher
torques needed to accelerate the vehicle the heat generation also goes
up. The Ragussa pan is a passive device, but to some extent air flow
helps to transfer heat away from its surfaces. Actually, I have both- a
Ragussa pan and auxiliary cooler in front of the radiator- and I
wouldn't say she's over-cooled. If I ever decide to use a toad, I'm
going to go to a 3.42 final drive for sure.

Clark Searle
Mt. Pleasant, MI

> >
> >
> > > Is the reason for increased pan temperature in stop and go traffic
> because
> > > of no cooling air flow or because not enough tranny fluid is being
> > > circulated through the cooler?
> >
> > Hienz, I don't nearly qualify as a "tranny" expert, but I know that the
> two
> > reasons you mention both have a negative effect upon cooling, and that the
> > reason for most of the increase in temperature comes from the extra heat
> > that is generated whenever the transmission is "slipping." This occurs
> when
> > idling at a stop, and especially during starts, when the torque converter
> is
> > slipping to multiply the torque to the drive wheels. The best thing to do
> > when you have high transmission temperatures is to go easy on the
> throttle.
> >
> > Scott Shean
>
> I'll buy that Scott, but while the tranny is "slipping" is there still lots
> of fluid circulated through the cooler? is there a route back to the pan
> that doesn't go through the cooler, I.e. is only a portion of the tranny
> fluid being passed through the cooler?
>
> Sorry about the dumb questions (oops there arn't any dumb questions), but
> the tranny just seems like a magic black box to me that I'd like to figure
> out some so that I can help "it" to take care of my "me" and my GMC.
>
> If there is indeed only a portion of the fluid going through the cooler than
> the Ragusa Pan has much more value than originally thought.
>
> Heinz
 
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