External ATF cooler

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My late Dad used 4 door sedans with smaller V-8 engines , to pull their Airstream . Years ago , he and Mom came back from a fishing trip . It was hot summer . ( late 70's Ford LTD )

On the way to the lake , they were traveling in hilly country with the wind to their back . They blew the front / torque converter seal . Limped into the nearest town and had the seal replaced .

Dad asked the mechanic how to avoid that happening again . Dad was told to put an external transmission coil / fin cooler in front of the radiator .

They made it to the lake and back home w/o incident . Dad had learned to be mindful of the conditions that had caused the seal to blow .

Soon after they returned home , they came to our house . Dad asked if I would help him install an external cooler . I told him sure , be glad to . I asked if he had any idea where would be the best store to purchase on from . He did not know and I had no idea , either .

We called a local , near by , Checker auto parts store ( long since closed ) which I had purchased odds and ends , from . Yes , they stocked them . Away we went to go shopping . They had several . I asked Dad which one he thought would be appropriate . He said he did not know , so thought to get the largest .

The LTD had the conventional cooler in the radiator tank with 2 ATF lines attached . We asked if it made any difference which of those 2 lines to hook the external cooler to . We were told to hook it to the line coming from the transmission ( the hotter of the 2 ) , not the line returning ATF from the radiator cooler to the transmission ( the cooler of the 2 ) .

The guy at the parts store told us , in the winter , the ATF passing through the radiator ( after it had passed through the external cooler ) would warm the ATF up to " normal operating temperature " due to the heat from the antifreeze / engine coolant . And the transmission would be " happier " with ATF at that temperature .

Does anyone know if that is correct , or just an old wives tale ?

Dad and I installed an external transmission cooler , on the next car they purchased , also . A 1991 Chevy Caprice 5.0l 4 door sedan .

Never had any more transmission problems .

Thanks , :)
Wyr
 
Not in my experience …
I always buy TruCool LPD and they want the cooler radiator line to feed the stack plates.
They have asymmetrical passages so that cold/thicker ATF will bypass and as it gets hot further penetrating the stacks.
 
Yes, the lines internal to the radiator can be though of as "temperature regulating lines." In the Winter, they serve to help heat the ATF to operating temperature and in the Summer, they provide some cooling capacity, although not much.

If you intend to retain the lines in the radiator, you should run the lines like this:

output from tranny > inlet of external cooler > outlet of cooler to input of radiator > outlet of rad to inlet of tranny
 
Originally Posted by thastinger


If you intend to retain the lines in the radiator, you should run the lines like this:

output from tranny > inlet of external cooler > outlet of cooler to input of radiator > outlet of rad to inlet of tranny


That was what I was trying to say , however it probably did not come out as clearly as you put it .

Thanks , :)
 
Originally Posted by 4WD
Not in my experience …
I always buy TruCool LPD and they want the cooler radiator line to feed the stack plates.
They have asymmetrical passages so that cold/thicker ATF will bypass and as it gets hot further penetrating the stacks.

This is the way my cooler is hooked up. According to the directions, this most efficient for max cooling. I have never had problems in the winter.
 
If you live in Texas and want to keep it cool, run it in-line from the radiator output, so you're not re-heating the cooled fluid before it goes back into the tranny - same as 4wd and inspecktor said.

I have mine plumbed this way, and I have NO problem getting the fluid to it's normal operating temp, even down to 13F (coldest I have driven it in; milder climate here). I have a gauge installed measuring the temp in the pump area, so I have actual temp data on this, not just "nothing bad ever happened." Also, my cooler is +1 sized - e.g., the next size larger from my application vs. recommended.
 
I have the trans cooler on my Cherokee plumed in AFTER the radiator.

I want the fluid as cool as possible when I'm beating on the thing. Cooling it down with a trans cooler, then heating it back up in the radiator seems a bit counter productive.
 
Originally Posted by WyrTwister


The guy at the parts store told us , in the winter , the ATF passing through the radiator ( after it had passed through the external cooler ) would warm the ATF up to " normal operating temperature " due to the heat from the antifreeze / engine coolant . And the transmission would be " happier " with ATF at that temperature .

Does anyone know if that is correct , or just an old wives tale ?

Dad and I installed an external transmission cooler , on the next car they purchased , also . A 1991 Chevy Caprice 5.0l 4 door sedan .

Never had any more transmission problems .

Thanks , :)
Wyr

I have installed a Hayden 678 (perhaps too large) for the 97 Maxima after the radiator heat exchanger, and in real winter, the torque won't lock because the ATF is not warm enough - though cardboard in front of it rectifies this. Even in summer, engine braking down mountain passes with AC on, I loose engine braking in 3rd once the ATF gets cool enough. But at least I don't have to worry about it being too hot going up the mountain passes.
 
Originally Posted by WyrTwister
The guy at the parts store told us , in the winter , the ATF passing through the radiator ( after it had passed through the external cooler ) would warm the ATF up to " normal operating temperature " due to the heat from the antifreeze / engine coolant . And the transmission would be " happier " with ATF at that temperature .

Does anyone know if that is correct , or just an old wives tale ?


Thanks , :)
Wyr


The radiator tank cooler for AT fluid is on the cold side of the radiator. No way is it at normal operating temp or the car would be over heating. That being said it will loose some heat to the coolant once the trans fluid is hotter than the coolant. But don't depend on it to be making the fluid hotter in the winter.
 
Different parts of the state have different climates . Where I live it goes from below 0F ( occasionally ) to above 100F ( fairly often ) .

No matter which way you plumb the cooler , you are bound to be better off with it than without it . And I can see the logic of either method .

Thanks , :)
Wyr
 
I had a '97 Ford Taurus SHO that I added an external AT cooler from the earlier Taurus SHOs. It was a radiator style. Worked great but I had to lower the torque converter lock up temp to less than 150F or in the winter it would not lock up on the highway.
 
Which is why TruCool (Dana) came up with the clever LPD bypass system … it functions like a factory system until the ATF gets hot enough to thin and then penetrate more of the air cooled plates …
It's been used on many factory installations too …
 
I use Hayden 679 on my FJ Cruiser and have installed it after the radiator, they also make the same model aka Hayden 699 with built in thermostat in case you live in a very cold region but the warmed radiator fluid usually does the job of stabilizing the transmission fluid. If you use a synthetic ATF then you can do without the thermostat.
 
Originally Posted by thastinger
Yes, the lines internal to the radiator can be though of as "temperature regulating lines." In the Winter, they serve to help heat the ATF to operating temperature and in the Summer, they provide some cooling capacity, although not much.

If you intend to retain the lines in the radiator, you should run the lines like this:

output from tranny > inlet of external cooler > outlet of cooler to input of radiator > outlet of rad to inlet of tranny


Output from trans > into radiator > out of radiator > into external cooler > out of external cooler > into trans pan.

This is the right way.
 
Originally Posted by 4WD
Which is why TruCool (Dana) came up with the clever LPD bypass system … it functions like a factory system until the ATF gets hot enough to thin and then penetrate more of the air cooled plates …
It's been used on many factory installations too …

100%. This is how the factory does it... I would wager NEVER the other way.

Always, thru the rad tank cooler FIRST, and then thru the aux. cooler SECOND.

For wintertime season I would set up the external cooler so it can be totally bypassed. This can be done with valving for season-to-season convenience.
 
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By the way, when cutting-in to a transmission fluid cooler line (and with a desire to put Auto Transmission Fluid rated high quality hose, onto said lines) - you need to either "bead" the tubing line, or solder-on a brass ferrule - so that the clamp / line assembly will never, never come-off due to temp. and pressure. Part of the issue with adding-on a cooler relates to work on the car that is not up to Factory-snuff, by way of mechanical strength, robust nature, etc...
 
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Originally Posted by RoyFJ
I use Hayden 679 on my FJ Cruiser and have installed it after the radiator, they also make the same model aka Hayden 699 with built in thermostat in case you live in a very cold region but the warmed radiator fluid usually does the job of stabilizing the transmission fluid. If you use a synthetic ATF then you can do without the thermostat.



Do have a transmission cooler mounting pic?
 
I am contemplating using a heat sink vs a fin and tube cooler to cool the AT fluid in my 240 wagon.

The heat sink is an easy installation. The cooler is much more challenging.

Does anyone have experience with a heat sink cooler?

Sam
 
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