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Transmission oil coolers

Immortality

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No, it's the other way, I discovered this the first time I changed and flushed the fluid. That's a factory fitted cooling system. Trans> External Cooler> Rad> Trans.

That is weird, I'm fairly sure mine was trans -> radiator -> external -> trans. That's how it was when I replaced the flexi-hoses that were starting to perish and leak.
 

VR38

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Main thing when fitting a cooler is that the feed line is at the bottom and the return line is at the top.
 

Pollushon

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That is weird, I'm fairly sure mine was trans -> radiator -> external -> trans. That's how it was when I replaced the flexi-hoses that were starting to perish and leak.

Yeah, caught me by surprise because I assumed the same as you, but when I cranked it over to pump the fluid out I got a rude surprise and fluid all over the driveway instead of the container :) My VP (factory fitted) is the same.

Main thing when fitting a cooler is that the feed line is at the bottom and the return line is at the top.

Why? Holden did the opposite in both of mine and on the power steering too. Feed from trans to upper of external cooler to lower, then to upper of rad to lower, then back to trans. A quick google yields this is the case for most factory cooler routing.
 

Immortality

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You want the return coming from the coolest part of the radiator, so, the bottom of the radiator been cooler than the top it is best to feed hot fluid in the top and take cold fluid from the bottom.
 

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Are you being funny Ari? Either way both my factory fitted external cooling systems disagree with that and personally I would too.
 

VR38

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Feed to the bottom to help prevent drain back.
 

delcowizzid

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im with immortality external cooler after radiator.factory might do it so you get hotter quicker on first few km of driving but better cooling overall.i opt for the radiator knocking off the high temp coming out of the convertor and the external knocking off extra afterwards just makes sense on being the best way to remove the maximum heat especially with a high stall converter.i also feed both coolers from the bottom so they are allways gaurenteed to be full and free of air when fluid is pumping.it does put extra pressure in the hoses but ive never had issues. a lot of companies that sell externals and trans guys suggest running the external in parrelel with the factory
 

drewVHSS

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Does anyone know if the captiva boxes have a thermostat controlled cooling setup like some other transmissions do?
If it does, it wont allow flow to the cooler untill it reaches "operating" temperature anyway. If so, you can safely run an external only cooler if you want to.
If it doesn't control flow to and from the cooler, then it might be useful to have the factory one still in the cooling path.

As a rule of thumb i've always based whether the external cooler should be first or last should be dependant on where you live, if always cold climate but heavy towing, internal first and external 2nd.
vice versa if in hot climate, use the external to knock the heat out first and then hopefully the cooler tranny fluid will help the engines cooling system maintain a lower temp by pre warming the fluid to operating temp before returning to the box.
The rate of flow of the transmission fluid i believe should be fast enough that the much higher operating temp of the engines cooling system shouldn't raise the transmission fluid by much.

Something to have a think about....
The coolant in the radiator doesn't sit at all times at the same temp as the engine.
Think about it, the thermostat only opens when it reaches temp and then shuts again when temp falls below it's threshold.
Therefore, when the thermostat is shut, the coolant in the radiator that is still getting airflow to cool it down will always be cooler than the engine.
There may be a difference of 5-20 degrees between the coolant cycling in the engine vs the coolant held in the radiator.


Dunno if my conclusions from 15 years of tinkering is of any help or not...
 

Pollushon

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My thermostat is only shut for a few mins/kms on my daily drives, I spend more than half those trips in traffic with the thermo flicking on and off and the temp gauge averaging 1/3-1/2. There was just too much to think about, too much poor design and opinion, that's why I bypassed it and now bath in the glorious results according to my NTC, lol.
 
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