Transmission Fluid Flow Rate through Radiator problem?

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

> 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
>

I do not recall ever seeing a specification for transmission fluid flow rate
through the radiator. The flow rate will vary depending on pump output. I
would see if the coolant temperature drops after it exits the radiator and
cooler.
--

Ray O
(correct punctuation to reply)

wrote:
> 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
>
Every turn in a line, additional cooler, fittings, ect, will cause some
resistance in the hydraulic flow. Did the trans shop test the radiator
flow bypassing the additional cooler? I have never seen a hydraulic
cooler fail from the inside from corrosion, or buildup restrictions
except for component failure that restrict/plug the line with debris.
Make sure that the trans temp indicating system is operating correctly
like Ray said. Check the temp with an in line gauge. Check the actual
trans pump flow as well.

On Wed, 13 Jun 2007 16:00:45 -0500, "Ray O"
<rokigawaATtristarassociates.com> wrote:

>
> wrote in message
roups.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
>>
>
>I do not recall ever seeing a specification for transmission fluid flow rate
>through the radiator. The flow rate will vary depending on pump output. I
>would see if the coolant temperature drops after it exits the radiator and
>cooler.

I have not seen a flow rate either but I also agree the pump output
will variy some with engine RPM and is not a fixed rate. As mentioned
above the tempature drop is the bigger concern and if OP had over
heating tranny problems if engine was running hot too it would take
the tranny with it unless you had a aux external cooler. DO not get
carried away with aux cooler size though as many do because you can
overcool oil and reduce flow rate because oil is thicker when cooler.
-----------------
TheSnoMan.com

>
> I do not recall ever seeing a specification fortransmissionfluidflowrate
> through theradiator. Theflowratewill vary depending on pump output. I
> would see if the coolant temperature drops after it exits theradiatorand
> cooler.
> --
>
> Ray O
> (correct punctuation to reply)

Thanks Ray O,
Tranny shop said they tested t-fluid flow with "operating temp" fluid
using the same RPM's for three flow tests;
1) just tranny which produced 3 quarts in 30 sec.
2) tranny and aux-cooler which also produced 3 quarts in 30 sec.
3) tranny and radiator which produced just 1 quart in 30 sec.

Do not know if they had a measured both the in and out temps... will
ask.

Have to presume their logic is.... if there is a restriction or fault
in the radiator flow then the t-fluid will not cool... especially when
the tranny wants a 3 quart rate.

Thx
Dave-in-Denver

>
> I have not seen aflowrateeither but I also agree the pump output
> will variy some with engine RPM and is not a fixedrate. As mentioned
> above the tempature drop is the bigger concern and if OP had over
> heating tranny problems if engine was running hot too it would take
> the tranny with it unless you had a aux external cooler. DO not get
> carried away with aux cooler size though as many do because you can
> overcool oil and reduceflowratebecause oil is thicker when cooler.
> -----------------
> TheSnoMan.com

Thanks SnoMan,
I will ask about the in/out temp drop.

Engine has never run hot... temp gauge rarely varies once up to temp.

Have to presume that OP in tranny has been pushing against what we
presume to be a low flow problem in the radiator since the radiator
was new 2 years ago, and since the new tranny was rebuild 6 months
ago.
(FYI the new tranny work Soooo much better than the old one and it
still does.)

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.

Thx
Dave-in-Denver

> wrote in message
oups.com...
> >
>> I do not recall ever seeing a specification fortransmissionfluidflowrate
>> through theradiator. Theflowratewill vary depending on pump output. I
>> would see if the coolant temperature drops after it exits theradiatorand
>> cooler.
>> --
>>
>> Ray O
>> (correct punctuation to reply)
>
> Thanks Ray O,
> Tranny shop said they tested t-fluid flow with "operating temp" fluid
> using the same RPM's for three flow tests;
> 1) just tranny which produced 3 quarts in 30 sec.
> 2) tranny and aux-cooler which also produced 3 quarts in 30 sec.
> 3) tranny and radiator which produced just 1 quart in 30 sec.
>
> Do not know if they had a measured both the in and out temps... will
> ask.
>
> Have to presume their logic is.... if there is a restriction or fault
> in the radiator flow then the t-fluid will not cool... especially when
> the tranny wants a 3 quart rate.
>
> Thx
> Dave-in-Denver
>

If that is the case, then there is a problem in the radiator. The
transmission part of the radiator may have been rebuilt incorrectly, the
cooling fins are obstructed so that sufficient air does not flow through
them, or something has clogged the cooler part internally.
--

Ray O
(correct punctuation to reply)

>
> Every turn in a line, additional cooler, fittings, ect, will cause some
> resistance in the hydraulicflow. Did the trans shop test theradiatorflowbypassing the additional cooler? I have never seen a hydraulic
> cooler fail from the inside from corrosion, or buildup restrictions
> except for component failure that restrict/plug the line with debris.
> Make sure that the trans temp indicating system is operating correctly
> like Ray said. Check the temp with an in line gauge. Check the actual
> trans pumpflowas well.

Thanks Ph@Boy,
Well the old tranny sure had it problems and your comments make me
think that perhaps some debris from it could have caused the
restriction in the radiator. And that junk was not cleaned out as
part of the tranny job.... causing overheating and perhaps introducing
old debris into my new tranny.... Yuck.

Good suggestion to test the tran temp sensor... I will ask.

Check the actual tranny pump flow... well I guess that the tranny shop
was happy with the 3 quarts in 30 seconds... but I will ask them if it
actually meets volume and SPI specs.

Thx
Dave-in-Denver

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

On Wed, 13 Jun 2007 16:16:53 -0700, wrote:

>Check the actual tranny pump flow... well I guess that the tranny shop
>was happy with the 3 quarts in 30 seconds... but I will ask them if it
>actually meets volume and SPI specs.


This sounds high for a tranny at idle. Nominal flow rate would depend
a lot on trany size and isle speed and oil cooler line size to. If you
are really worried you could install a pressure gauge on tranny line
in a "Tee" to test it. Check pressure before cooler and after and if
there is a restriction in cooler you will see a big pressure
differentail.
-----------------
TheSnoMan.com