Bypassing factory cooler altogether?

[FL_Rob]

Has anyone here routed aux cooler/lines to an area completely away from any other sources of heat,engine radiator anything.Iwas thinking of taking it to the( non-exhaust )side frame rail, using a 22000 cooler and spin on filter relocating kit.I will now sit back for all input.Vehicle is '93 Chevy G20.
I just cant wrap my brain around why they would route cooler lines by a source of greater heat.Could overcooling with this setup be a prob?

 

[MrHorspwer]

I assume you're talking about a trans or aux. oil cooler?

You put coolers in the front of the vehicle because that's where the airflow is. A typical tube and fin heat exhanger needs air to pass over it with some velocity to evacuate the heat. Without airflow, the cooler will just sit and soak up all the latent heat.

If you're looking for do an under-vehicle cooler location and want to see results, you'll need a fan on the aux. cooler. It's not really all that uncommon. Street rodders have been using small frame mounted trans coolers with an attached cooling fan since there typically isn't enough room in the front of the vehicle. There simply isn't enough airflow under the vehicle to effectivly cool without a fan.

 

[Audi Junkie]

Often one system is used to heat another. Oil cooler is also an oil warmer when it's an intercooler. I wouldn't mess with a system that is oem tested to a state of thermal equilibrium.

 

[exranger06]

The factory cooler is actually a VERY efficient unit. You can add an additional cooler if you'd like, but it would be a downgrade to remove the factory one from the system.

 

[FL_Rob]

Ok,i've been convinced,I'll just ADD an additional cooler inline with the factory setup.I usually do it like this anyway on previous vehicles and have had no problems , just kickin' some ideas around for longevity.Thanks to all for your ideas on this .

 

[cchase]

I'm going to have to say that the best idea (assuming we're talking about adding on an auxiliary transmission cooler) is that if currently the transmission is cooled by the radiator, to bypass that entirely. Stock thermostat is 195 degrees which means the radiator is effectively 195 degrees... way too hot for ATF.

The only wildcard in my mind is that I think 3/4 ton vans already had a factory auxiliary transmission cooler.

 

[MrHorspwer]

Quote:
Stock thermostat is 195 degrees which means the radiator is effectively 195 degrees... way too hot for ATF.


Manufacturers disagree.

From TCI:
http://www.tciauto.com/Products/TechInfo/trans_life_expectancy.asp

"The ideal operating temperature for automatic transmission fluid is between 175 and 225° F."

They go on to say that really bad things start happening at about 240° F.

 

[Gary Allan]

Yeah. The trans cooler in the rad is not seeing 195F unless the engine is overheating. Liquid:liquid exchangers are WAY more efficient than air:liquid exchangers. You don't need nearly the temp differential to exchange more heat. Some Toyota trucks don't use a radiator embedded cooler. They route the engine coolant directly to the trans. If they have an auxiliary cooler, it is a separate radiator up front, but only works when the converter is unlocked. Otherwise, the engine coolant (direct) handles it all.

 

[cchase]

Originally Posted By: MrHorspwer
Quote:
Stock thermostat is 195 degrees which means the radiator is effectively 195 degrees... way too hot for ATF.


Manufacturers disagree.

From TCI:
http://www.tciauto.com/Products/TechInfo/trans_life_expectancy.asp

"The ideal operating temperature for automatic transmission fluid is between 175 and 225° F."

They go on to say that really bad things start happening at about 240° F.


By that chart, 195 degree transmission fluid only makes a transmission last 50,000 miles and 220 degree fluid lasts 20,000 miles. Not really great lifespan.

Compare to 175 degrees at 100,000 miles.

 

[cchase]

Originally Posted By: Gary Allan
Yeah. The trans cooler in the rad is not seeing 195F unless the engine is overheating. Liquid:liquid exchangers are WAY more efficient than air:liquid exchangers. You don't need nearly the temp differential to exchange more heat. Some Toyota trucks don't use a radiator embedded cooler. They route the engine coolant directly to the trans. If they have an auxiliary cooler, it is a separate radiator up front, but only works when the converter is unlocked. Otherwise, the engine coolant (direct) handles it all.


I don't know enough about it but if the radiator transmission oil coolers are the correct solution why do all HD transmissions have transmission oil coolers that specifically do not use the coolant radiator?

I'm just trying to learn, but as an additional question, I understand that liquid:liquid is better than liquid:air but essentially using coolant to "cool" transmission fluid is still a liquid:air since the coolant is still a liquid:air and the coolant, even exiting the radiator, is probably still in the mid 100's.

 

[cchase]

My only experience which is not an apples to apples comparison is the difference between a 3/4 ton truck with an auxiliary transmission cooler and my own truck which does not. In my truck, normal driving on a summer day gives transmission temperatures in the high 190's to low 200's. On the truck with an auxiliary transmission cooler under similar duty, transmission temperatures never exceed 130 degrees, using a liquid:air radiator in front of the coolant radiator.

 

[cchase]

Quote:
While the stock transmission cooler may be adequate for normal driving, additional cooling is needed when pulling a trailer, carrying a heavy load, climbing hills, traveling in hot weather, and so forth. With vehicle radiator temperatures normal ly at 180 to 220 degrees F, ATF cooling is marginal. For instance, if ATF enters the radiator cooler at 300 degrees F under severe conditions it may leave at 240 to 270 degrees F., which is not anywhere sufficient for extended fluid life.


From http://newcarbuyingguide.com/index.php/news/main/3066/event=view

Quote:
Therefore, an auxiliary transmission oil cooler, a separate radiator that generally mounts in front of the regular radiator is needed. While a cooler is pretty much a must for trailer towing, they are a good investment if you live in a hot climate, or pull a heavy load like a large family, or a carpool with many passengers.


Tubing carries hot ATF to this radiator, while return lines deliver cooler fluid back to the transmission. The best way to obtain an auxiliary cooler is to order a vehicle with an auxiliary cooler already installed. For instance, most towing packages includes one. If not, an auxiliary transmission fluid cooler is relatively easy to install on most vehicles.

 

[JustinH]

Many transmission shops will either replace the radiator when the transmission is replaced due to failure, or they will plumb a cooler around the radiator to avoid pushing sludge/metal into the new transmission.

If you live in the south, I wouldn't see a problem eliminating the factory heat exchanger if you have to, but up north you need the radiator to warm up the fluid.

 

[calvin1]

Originally Posted By: Gary Allan
Yeah. The trans cooler in the rad is not seeing 195F unless the engine is overheating. Liquid:liquid exchangers are WAY more efficient than air:liquid exchangers. You don't need nearly the temp differential to exchange more heat. Some Toyota trucks don't use a radiator embedded cooler. They route the engine coolant directly to the trans. If they have an auxiliary cooler, it is a separate radiator up front, but only works when the converter is unlocked. Otherwise, the engine coolant (direct) handles it all.


Adding to this all the coolant>atf exchangers I've seen were on the COLD end of the radiator. The transmission gets dibs on the coolant before the engine gets a crack at it. If there's no temp drop across the radiator you have worse problems than a hot transmission and should really be waiting on the side of the road for a wrecker instead.

 

[mechtech2]

cchase The 195 thermostat temperature is NOT the radiator's temperature. Only on certain rare situations.

 

[cchase]

Originally Posted By: mechtech2
cchase The 195 thermostat temperature is NOT the radiator's temperature. Only on certain rare situations.


Right, it's only the temp of the coolant as it enters the radiator, it should be lower on the output side of the radiator. If I understand it all correctly.

 

[440Magnum]

Originally Posted By: cchase

I don't know enough about it but if the radiator transmission oil coolers are the correct solution why do all HD transmissions have transmission oil coolers that specifically do not use the coolant radiator?

I'm just trying to learn, but as an additional question, I understand that liquid:liquid is better than liquid:air but essentially using coolant to "cool" transmission fluid is still a liquid:air since the coolant is still a liquid:air and the coolant, even exiting the radiator, is probably still in the mid 100's.


All HD installations I'm aware of have an additional oil-to-air cooler that comes AFTER the oil-to-water cooler in the radiator. The oil-to-water cooler is far more efficient and actually takes most of the heat out of the transmission fluid, the oil-to-air cooler is just more margin.

Transmissions are actually pretty tolerant of a wide range of temps, especially with good synthetic fluids. They should live forever at anything under 250F.

 

[cchase]

Originally Posted By: 440Magnum
Originally Posted By: cchase

I don't know enough about it but if the radiator transmission oil coolers are the correct solution why do all HD transmissions have transmission oil coolers that specifically do not use the coolant radiator?

I'm just trying to learn, but as an additional question, I understand that liquid:liquid is better than liquid:air but essentially using coolant to "cool" transmission fluid is still a liquid:air since the coolant is still a liquid:air and the coolant, even exiting the radiator, is probably still in the mid 100's.


All HD installations I'm aware of have an additional oil-to-air cooler that comes AFTER the oil-to-water cooler in the radiator. The oil-to-water cooler is far more efficient and actually takes most of the heat out of the transmission fluid, the oil-to-air cooler is just more margin.

Transmissions are actually pretty tolerant of a wide range of temps, especially with good synthetic fluids. They should live forever at anything under 250F.


That's very good to know. This issue is very timely for me as I just ordered a transmission cooler and didn't specifically know if I should run it after the radiator or just eliminate the radiator altogether.

I wish what you said about the transmission lasting was true for the 4L60E. Unfortunately I'm on my 4th one.

 

[Gary Allan]

Originally Posted By: cchase
Originally Posted By: Gary Allan
Yeah. The trans cooler in the rad is not seeing 195F unless the engine is overheating. Liquid:liquid exchangers are WAY more efficient than air:liquid exchangers. You don't need nearly the temp differential to exchange more heat. Some Toyota trucks don't use a radiator embedded cooler. They route the engine coolant directly to the trans. If they have an auxiliary cooler, it is a separate radiator up front, but only works when the converter is unlocked. Otherwise, the engine coolant (direct) handles it all.


I don't know enough about it but if the radiator transmission oil coolers are the correct solution why do all HD transmissions have transmission oil coolers that specifically do not use the coolant radiator?


The use of liquid:liquid is more compact. If you've got the room or cannot use a big enough radiator to handle the additional load, then a separate rad cooler might be in order. It will tend to be a bigger one if there's not a coolant:fluid exchanger in the mix too.


Quote:

I'm just trying to learn, but as an additional question, I understand that liquid:liquid is better than liquid:air but essentially using coolant to "cool" transmission fluid is still a liquid:air since the coolant is still a liquid:air and the coolant, even exiting the radiator, is probably still in the mid 100's.


Sure. Look at the size and depth of your radiator. It has many gallons per minute of flow potential. It has induced air flow if there's no ram air to cool it.

There's nothing wrong with the mid 100's and the fluid is probably returning at a higher temp ..maybe 175F (who knows?).

The best setup, imo, would be to use a thermostat using only 3 ports. You would then bypass the auxiliary cooler below 180F and modulate it in line as it exceeded 180F. You could run it either before or after the in rad heat exchanger depending on if you needed to unload the rad ..or wanted to regulate the return temp to around 180F+/-

 

[mechtech2]

Use the stock cooler, and from there go to your aftermarket one, then back to the trans.
In winter, block the aftermarket one with cardboard or similar.