Which side of the radiator does the trans cooler lines go into?

So I have learned some interesting things from a ford(haha) but also GM transmission engineer(former, rather) and when it came to my f150, the transmission cooler goes on the passenger side, where the cap is aswell, and he convincingly dispelled the idea the trans needs to run into the radiator during winter because that side remains much colder, almost ambient, and in winter conditions, the trans "cooler" will just remain being a "cooler" and having an auxillary cooler in front of the rad with a cover will achieve the same "cooling" as the in-tank trans cooler most stock vehicles have.

However, Its still kinda blowing my mind I guess and I guess it then demands asking which side the trans cooler is on any given application and then asking if that is indeed the cold side of the radiator(I assume the cap is always on that side, but hell if I know)
Im gonna go out on a limb and guess that the lower radiator hose in a cross flow radiator is where the "cold" side is.

Anyway, If this happens to be true, that means bypassing a radiator end tank shouldnt be harmful, however, it must be noted that liquid to liquid heat transfer is still more efficient than doing a small aftermarket radiator in front of your condensor/radiator but if you size it right, it shouldnt matter.

This may also explain why when I replaced the 2001 mercury grand marquis radiator I stabbed with a screwdriver long ago that ford didnt even use the end tank, but rather a small rad mounted inbetween the condensor and radiator.

I dont have an automatic transmission in my square but curious if anyones ever tried or has thoughts on this.

NV4500 swap and never worry about slushbox and its silly hoses.

Passenger side.

SquareRoot said:

NV4500 swap and never worry about slushbox and its silly hoses.

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If you're offering

plus my sm465 doesnt need any silly hoses, but the automatics in my life are ****** like that.

At least some of the diesel equipped squares have the lines on the driver side.

AKguy said:

At least some of the diesel equipped squares have the lines on the driver side.

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Do their radiators flip which side has the upper/lower hose and the cap?

Also, do they also use an oil cooler for engine oil in the opposite tank?

All trans coolers are on the cold side of the radiator... ALWAYS. Its a basic function of heat transfer. You only lose about 100 degrees of coolant temp(or less) between the hot and cold sides of the radiator on most applications. Diesels, big blocks, and heavy tow vehicles will almost always have an engine oil cooler on the hot side of the radiator.

You can use a temp gun to see the actual temps on everything and see that your former engineer you talked to is wrong. My 2011 Suburban at operating temps showed ~180 degrees at the hot side of radiator, ~100 degrees on the cold side, ~70 degrees on the cooler line from trans to radiator, ~120 degrees out of radiator to external cooler. Your transmission temps need to be over 100 degrees for proper operation, but you want them to stay well under 200. Engine oil temps run in the 230+ degree range and can be over 260 in a high performance or heavy towing engine, which is why they run the engine oil cooler on the hot side. You want it to be hot enough to boil off any moisture, but not so hot the oil starts breaking down.

Bextreme04 said:

All trans coolers are on the cold side of the radiator... ALWAYS. Its a basic function of heat transfer. You only lose about 100 degrees of coolant temp(or less) between the hot and cold sides of the radiator on most applications. Diesels, big blocks, and heavy tow vehicles will almost always have an engine oil cooler on the hot side of the radiator.

You can use a temp gun to see the actual temps on everything and see that your former engineer you talked to is wrong. My 2011 Suburban at operating temps showed ~180 degrees at the hot side of radiator, ~100 degrees on the cold side, ~70 degrees on the cooler line from trans to radiator, ~120 degrees out of radiator to external cooler. Your transmission temps need to be over 100 degrees for proper operation, but you want them to stay well under 200. Engine oil temps run in the 230+ degree range and can be over 260 in a high performance or heavy towing engine, which is why they run the engine oil cooler on the hot side. You want it to be hot enough to boil off any moisture, but not so hot the oil starts breaking down.

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Well to be fair the coolant flow on your 2011 is suburban is very unique because doesnt it have a purge and overflow tank, and a bypass line to the cold side as well? i dont know how those all interact on that, but I have looked more into it, the idea is that the trans within short time starting the vehicle and using it will be heating the coolant as it will exceed the cold-sides temp in short time.
However, could the heat gun be influenced by the engine bay, cramped area, external heat transfer on the metal(unless syou pointed it at the plastic tank)
On his claims, he used thermocouples.

his name is mark kovalsky if it means anything. I am preppared to test out the idea myself this coming winter. I need to replace my radiator anyway since the plastic end tank on side weeps and

I had to negotiate some line that wouldnt cooperate.

But if you want to see what I did till then

AuroraGirl said:

Well to be fair the coolant flow on your 2011 is suburban is very unique because doesnt it have a purge and overflow tank, and a bypass line to the cold side as well? i dont know how those all interact on that, but I have looked more into it, the idea is that the trans within short time starting the vehicle and using it will be heating the coolant as it will exceed the cold-sides temp in short time.
However, could the heat gun be influenced by the engine bay, cramped area, external heat transfer on the metal(unless syou pointed it at the plastic tank)
On his claims, he used thermocouples.

his name is mark kovalsky if it means anything. I am preppared to test out the idea myself this coming winter. I need to replace my radiator anyway since the plastic end tank on side weeps and

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I had to negotiate some line that wouldnt cooperate.

But if you want to see what I did till then

You must be registered for see images attach

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The specific layout of the cooling system shouldn't have much to do with the cooling theories at work here. Yes it is a closed system... no it isn't much different functionally from my squarebody. I can do the same test on my K25 if it makes you feel better. I'm running an in tank cooler and an external on mine.

Maybe he was working with old non-lockup transmissions that run much hotter? We towed our travel trailer out to the coast this weekend. Unloaded driving around town, the trans runs around 100-120 degrees no matter what the outside temps are. Loaded going 65mph down the freeway it was running about 130 degrees and usually runs about 60-80 degrees above ambient. Torque converter unlocked and pulling up a steep grade through the coastal mountains it got a whopping 10 degrees warmer.

This same vehicle previously had no external cooler and no engine oil cooler(I upgraded to a full OEM heavy cooling package a couple years ago) and it would run in the 165-185+ temp range regularly towing a small pop-up trailer but was almost the same temps around town as it is now. The external cooler has kept the high temps under control and makes it cool down MUCH faster after I finish pulling a grade, but the around town temps and cold weather temps are almost identical.

Bextreme04 said:

The specific layout of the cooling system shouldn't have much to do with the cooling theories at work here. Yes it is a closed system... no it isn't much different functionally from my squarebody. I can do the same test on my K25 if it makes you feel better. I'm running an in tank cooler and an external on mine.

Maybe he was working with old non-lockup transmissions that run much hotter? We towed our travel trailer out to the coast this weekend. Unloaded driving around town, the trans runs around 100-120 degrees no matter what the outside temps are. Loaded going 65mph down the freeway it was running about 130 degrees and usually runs about 60-80 degrees above ambient. Torque converter unlocked and pulling up a steep grade through the coastal mountains it got a whopping 10 degrees warmer.

This same vehicle previously had no external cooler and no engine oil cooler(I upgraded to a full OEM heavy cooling package a couple years ago) and it would run in the 165-185+ temp range regularly towing a small pop-up trailer but was almost the same temps around town as it is now. The external cooler has kept the high temps under control and makes it cool down MUCH faster after I finish pulling a grade, but the around town temps and cold weather temps are almost identical.

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Well he said he was using the same transmission as I have(E4OD, the 4l80e but worse but go forder of ford transmissions in the 90s.)
Which is a C6 with an overdrive unit stuffed in the case behind it. has lock up and becuase of factory trans line diameters, tends to run hot on the diesels or the f250/f350 applications. (they fixed it when they made it into the 4r100)

But Im not sure we have the same exact idea, what im saying is that as it stands, I have an external cooler in place of the radiator tank.

His claim, and what I bring up, is he says that if I cover that cooler in the winter time, I will not harm the trans insofar that it will heat up and operate normally even tho its not in the side tank.
And that, there is no reason to have it piped into the side tank and the auxillary cooler unless the side tanks cooling ability was also needed in addition to the auxillary cooler.


Being that my cooler was choking my trans and the stuff that came out was yummy looking, I am not going to re use that until I replace the radiator. I havent been able to get the thing over 150 the last 4 days Ive drove it , when I was approaching 200 before (rip)

The only thing I should mention is that despite being a 96, my f150 doesnt have a reverse flow cooling system like how TBI sbc went. My serpentine belt in the end drives all the accessories the same direction minus I think the smog pump which doesnt care iirc. not sure if that matters.

AuroraGirl said:

Well he said he was using the same transmission as I have(E4OD, the 4l80e but worse but go forder of ford transmissions in the 90s.)
Which is a C6 with an overdrive unit stuffed in the case behind it. has lock up and becuase of factory trans line diameters, tends to run hot on the diesels or the f250/f350 applications. (they fixed it when they made it into the 4r100)

But Im not sure we have the same exact idea, what im saying is that as it stands, I have an external cooler in place of the radiator tank.

His claim, and what I bring up, is he says that if I cover that cooler in the winter time, I will not harm the trans insofar that it will heat up and operate normally even tho its not in the side tank.
And that, there is no reason to have it piped into the side tank and the auxillary cooler unless the side tanks cooling ability was also needed in addition to the auxillary cooler.


Being that my cooler was choking my trans and the stuff that came out was yummy looking, I am not going to re use that until I replace the radiator. I havent been able to get the thing over 150 the last 4 days Ive drove it , when I was approaching 200 before (rip)

The only thing I should mention is that despite being a 96, my f150 doesnt have a reverse flow cooling system like how TBI sbc went. My serpentine belt in the end drives all the accessories the same direction minus I think the smog pump which doesnt care iirc. not sure if that matters.

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It will heat up faster going through the radiator, but I agree you should be fine in the winter to just have the external cooler covered(unless its stupid -40 degree weather or something). The engine produces far more heat than a properly functioning automatic transmission does. Also, you will be regulating the temperature(both hot and cold) by running it through a radiator cooler as opposed to an external cooler where the running temp can vary much more based on ambient temp.

Bextreme04 said:

It will heat up faster going through the radiator, but I agree you should be fine in the winter to just have the external cooler covered(unless its stupid -40 degree weather or something). The engine produces far more heat than a properly functioning automatic transmission does. Also, you will be regulating the temperature(both hot and cold) by running it through a radiator cooler as opposed to an external cooler where the running temp can vary much more based on ambient temp.

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Im probably going to see how well it does pulling trailer(since I have good hills where I would be pulling too) and see how it does, If it handles I will prob put off radiator till next year if not Ill suck it up for a radiator this year lol. I need a new fan clutch too but not because its bad, its just a cheap autozone one so it can never decide if its 100% or barely turning often when idling or going low speed. sound like an aircraft sometimes lol

AuroraGirl said:

Im probably going to see how well it does pulling trailer(since I have good hills where I would be pulling too) and see how it does, If it handles I will prob put off radiator till next year if not Ill suck it up for a radiator this year lol. I need a new fan clutch too but not because its bad, its just a cheap autozone one so it can never decide if its 100% or barely turning often when idling or going low speed. sound like an aircraft sometimes lol

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Have you tried running cooler flush through the trans cooler in the radiator? Run it from the outlet to the inlet so it back-flushes.. let it sit on there for a few minutes, then hit it again, then hit it with compressed air and I bet you get a bunch of junk flying out of it. The outlet from your pump can be up in the 200psi range, so I wouldn't worry about compressed air blowing anything up

See the metal fitting on the radiator? And the tubing cutter? lol. I was trying to undo the fitting so I could fix the situation. But the cooler pipe was kinked and collapsed about where the tubing cutter was, and i could not get the fitting to budge, and the line right at the connection was a little soft from rust. So I just pinched it off with a pliers, cut the tube wherre It was not collapsed, flared, and clamped on hose and ran to cooler. The end tank fitting has to come out to ever try and fix. But after doing that, a lot of black stuff oozed out and I had already flushed a good amount of crud from it. THe cooling system, also, had been a little on the rusty corroded side (whoops) from my hard tap water use over time. I recently flushed it very well and got clean distilled+coolant in it, but that made me realize the integrity of the cooler possibly would be worrisome even if I did get the fitting off.

It all kinda culminates to why i wasnt too hard up choosing to do what I did lol. radiator weeps, fittings rusted in, lines kinked right at the fitting area, rusty/nasty coolant so who knows what condition internally it may have been. nasty was inside the cooler after clearing it out already, had a trans cooler in a box, need to follow up cooling system flush in the future with new rad hoses, new rad, new clamps(lower hose) fan clutch.. etc...
its a ford sadly. they need help