Transmission Fluid Flow Rate through Radiator problem?

I don't know what the flow rate should be, but if you have installed an aux
cooler, then you do not need to push the fluid through the radiator anymore,
making the flow rate a moot point.

As a test, try connecting the transmission directly to the aux cooler, and
leaving the radiator out of the circuit. If the transmission is pushing
several quarts per minute without the radiator in line, and only 2 quarts
per minute WITH the radiator connected, then leave the radiator disconnected
....

The diminished flow of fluid would certainly contribute to the overheating,
so you are on the right track.





> wrote in message
oups.com...
> My new transmission is (still) overheating on long highway drives.
>
> Transmission shop tested the t-fluid flow rate through the radiator at
> 1 quart every 30 seconds.
> The transmission itself however will push times that amount, 3 quarts
> every 30 seconds, all by itself and also through an aux t-cooler.
>
> My radiator is only 2 years old. When I first started having
> transmission overheating I found the radiator was shot and had it
> replaced and later put in a tran cooler too.
>
> So the questions is...
> What should be the t-fluid flow rate through the radiator?
> In other words... is my radiator restricting t-fluid flow rates below
> spec?
>
> 1993 4Runner, V6 3L, Auto, 4x4, 170K
>
> Thx
> Dave-in-Denver
>

Most of the heat generated by an automatic transmission comes from the inefficient torque converter. On long highway drives this should not happen if the torque converter lockup clutch is working.

wrote:
>
> My new transmission is (still) overheating on long highway drives.

--
Mike Walsh
West Palm Beach, Florida, U.S.A.

On Jun 14, 8:33 am, "Jeff Strickland" > wrote:
> I don't know what the flow rate should be, but if you have installed an aux
> cooler, then you do not need to push the fluid through the radiator anymore,
> making the flow rate a moot point.
>
> As a test, try connecting the transmission directly to the aux cooler, and
> leaving the radiator out of the circuit. If the transmission is pushing
> several quarts per minute without the radiator in line, and only 2 quarts
> per minute WITH the radiator connected, then leave the radiator disconnected
> ...
>
> The diminished flow of fluid would certainly contribute to the overheating,
> so you are on the right track.
>
> > wrote in message
>
> oups.com...
>

Thanks Jeff,
My brain had this idea too... maybe on a temporary basis.

BUT... but another poster indicated that bypassing the radiator
completely and just using the aux cooler would not be a good idea.
What do you think about post #7?

Thanks for you comments
Dave-in-Denver

On Jun 14, 8:50 am, Mike Walsh > wrote:
> Most of the heat generated by an automatic transmission comes from the inefficient torque converter. On long highway drives this should not happen if the torque converter lockup clutch is working.
>
> wrote:
>
> > My new transmission is (still) overheating on long highway drives.
>
> --
> Mike Walsh
> West Palm Beach, Florida, U.S.A.

Thanks Mike,
Now this sounds really interesting. It was my torque converter that
was really shot before I had it (and the tranny) rebuild.

I will ask the tranny shop if we have a chicken & egg situation here.
Torque converter causing heat... or even low t-fluid flow that causes
the torque converter to not cool and thus over heat.

Thanks
Dave-in-Denver

"Jeff Strickland" > wrote in message
news:Akcci.7414$pd5.1392@trnddc02...
>I don't know what the flow rate should be, but if you have installed an aux
>cooler, then you do not need to push the fluid through the radiator
>anymore, making the flow rate a moot point.
>

Without knowing how much cooling capacity the auxiliary cooler has, I would
not recommend permanently disconnecting or bypassing the radiator.
--

Ray O
(correct punctuation to reply)

"Ray O" <rokigawaATtristarassociatesDOTcom> wrote in message
vers.com...
>
> "Jeff Strickland" > wrote in message
> news:Akcci.7414$pd5.1392@trnddc02...
>>I don't know what the flow rate should be, but if you have installed an
>>aux cooler, then you do not need to push the fluid through the radiator
>>anymore, making the flow rate a moot point.
>>
>
> Without knowing how much cooling capacity the auxiliary cooler has, I
> would not recommend permanently disconnecting or bypassing the radiator.



I agree to a point.

It is important as to what the vehicle is doing when the trans gets hot, but
assuming normal loading and highway usage, the aux cooler should be more
efficient than the radiator, especially if the radiator is clogged so badly
that the flow is reduced by a factor of 3 or more.

There is much we don't know here, but if it was me having the trouble, I'd
test the theory that the radiator is clogged by removing the radiator from
the system. It should be easy enough to install some hoses that allow a
direct connection of the transmission to the aux cooler without permanently
altering the plumbing that is already in place. As part of the test, I'd
simply connect both of the radiator hose bibs together so any fluid that
might be inside the radiator does not come out and make a mess. Whatever
fluid is there would be a small amount though, and any mess would be limited
to the contents of the coils are inside the radiator.

On Thu, 14 Jun 2007 08:19:34 -0700, wrote:

>On Jun 14, 8:33 am, "Jeff Strickland" > wrote:
>> I don't know what the flow rate should be, but if you have installed an aux
>> cooler, then you do not need to push the fluid through the radiator anymore,
>> making the flow rate a moot point.
>>
>> As a test, try connecting the transmission directly to the aux cooler, and
>> leaving the radiator out of the circuit. If the transmission is pushing
>> several quarts per minute without the radiator in line, and only 2 quarts
>> per minute WITH the radiator connected, then leave the radiator disconnected
>> ...
>>
>> The diminished flow of fluid would certainly contribute to the overheating,
>> so you are on the right track.
>>
>> > wrote in message
>>
>> oups.com...
>>
>
>Thanks Jeff,
>My brain had this idea too... maybe on a temporary basis.
>
>BUT... but another poster indicated that bypassing the radiator
>completely and just using the aux cooler would not be a good idea.
>What do you think about post #7?
>

Which poster said that? Utter hogwash, there is no reason not to
remove the radiator cooling loop and use an aux cooler. Larger trucks
have been doing that for years, and very successfully, too. Result is
that the transmission runs *much* cooler (often times the radiator is
heating the ATF, not cooling it!) and you get better flow rates.

BTW, what is post #7? Is that like love potion #9?

On Thu, 14 Jun 2007 08:23:49 -0700, wrote:

>On Jun 14, 8:50 am, Mike Walsh > wrote:
>> Most of the heat generated by an automatic transmission comes from the inefficient torque converter. On long highway drives this should not happen if the torque converter lockup clutch is working.
>>
>> wrote:
>>
>> > My new transmission is (still) overheating on long highway drives.
>>
>> --
>> Mike Walsh
>> West Palm Beach, Florida, U.S.A.
>
>Thanks Mike,
>Now this sounds really interesting. It was my torque converter that
>was really shot before I had it (and the tranny) rebuild.
>
>I will ask the tranny shop if we have a chicken & egg situation here.
>Torque converter causing heat... or even low t-fluid flow that causes
>the torque converter to not cool and thus over heat.
>

Most cooling loops work like this:

Fluid from pump goes to torque converter.
From torque converter it goes to the cooler.
From the cooler it goes to bearings and other similar tasks.

Some fluid from the pump is bypassed to run the controlling servos and
valves. That fluid is dumped back into the pan.

Any aux cooler of sufficient capacity will work just fine, you don't
need the one in the radiator. IIRC the original post said this was a
small(er) truck, right? ANd if you are worried about AFT temperature,
get a temp guage installed and monitor the ATF temp in the pan. (No,
there is no use in monitoring the ATF temp to the cooler, as that
reflects the heat from the torque converter...) Measure the pan ATF
temps. Ideally as cool as possible.

"SnoMan" > wrote in message
...
> On Wed, 13 Jun 2007 16:08:29 -0700, wrote:
>
> >Aux cooler was picked out by tranny shop... it looks smaller than what
> >I would have picked out... so my guess is that the tranny shop follows
> >your advise too and does not over do it on aux size.
>
>
> One tip here on aux cooler, make sure it is routed so fluid passes
> through radiotr core tube and then aux cooler, not the other way
> around and not bypassing tank cooler completely either.
> -----------------
> TheSnoMan.com

I only installed a cooler on one of my vehicles (but others have come from
the factory with coolers already installed). On this one, the instructions
said you could either install the cooler in series with the radiator cooler,
in place of the radiator cooler, or in parallel with it.

I chose the first of the three options, but later came to believe this was
not the best method. As another poster mentioned, any kink, bend or
extra bit of plumbing will add to the resistance to flow in a hydraulic
system. A parallel installation would appear to give the least resistance
to flow, while a series installation would give highest resistance.

One thing I am not in doubt about is the critical nature of tranny
temperature, and I would much rather have it overcool than overhot.

PeterD > wrote in
:

> On Thu, 14 Jun 2007 08:23:49 -0700, wrote:
>
>>On Jun 14, 8:50 am, Mike Walsh > wrote:
>>> Most of the heat generated by an automatic transmission comes from
>>> the inefficient torque converter. On long highway drives this should
>>> not happen if the torque converter lockup clutch is working.
>>>
>>> wrote:
>>>
>>> > My new transmission is (still) overheating on long highway drives.
>>>
>>> --
>>> Mike Walsh
>>> West Palm Beach, Florida, U.S.A.
>>
>>Thanks Mike,
>>Now this sounds really interesting. It was my torque converter that
>>was really shot before I had it (and the tranny) rebuild.
>>
>>I will ask the tranny shop if we have a chicken & egg situation here.
>>Torque converter causing heat... or even low t-fluid flow that causes
>>the torque converter to not cool and thus over heat.
>>
>
> Most cooling loops work like this:
>
> Fluid from pump goes to torque converter.
> From torque converter it goes to the cooler.
> From the cooler it goes to bearings and other similar tasks.
>
> Some fluid from the pump is bypassed to run the controlling servos and
> valves. That fluid is dumped back into the pan.
>
> Any aux cooler of sufficient capacity will work just fine, you don't
> need the one in the radiator. IIRC the original post said this was a
> small(er) truck, right? ANd if you are worried about AFT temperature,
> get a temp guage installed and monitor the ATF temp in the pan. (No,
> there is no use in monitoring the ATF temp to the cooler, as that
> reflects the heat from the torque converter...) Measure the pan ATF
> temps. Ideally as cool as possible.
>

I am sorry but you are so wrong. the fluid goes from the cooler right
back into the pan. Also the big trucks use a thermostat in the cooler so
the fluid does not get over cooled. The reason the rad is suppsted to
always be after the aux cooler is to prevent overcooling in colder
weather. KB

--
Thunder Snake #9
"Protect" your rights or "lose" them.