Bypassing factory tranny cooler

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ARB1977

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Hey fellas,
Im reading some posts on other forums about bypassing the factory radiator transmission cooler with a aux cooler that has a interal bypass for winter months. Ive been reading were some have experienced radiator coolers bursting causing atf and radiator fluid to be mixed. Guys are having to fork over thousands of dollars for new transmissions and radiators.

How wise is this? On my Tacoma im running a TRD style cooler...nothing special after the stock radiator cooler. Ive been doing this for most of my trucks life but im alittle concerned down the road problems could happen. The TRD cooler does not have an internal bypass so i may get rid of that with one that does.

What are your thoughts.
 
On my Santa Fe they run the transmission lines into the radiator and then out from there into an auxiliary cooler and then back to the transmission. I guess this helps balance the heat/cold???
 
I would never bypass a factory trans cooler that goes in the radiator.
ESPECIALLY in winter!
That is when you need the heating that it provides for a better warm up the most!
Always run the trans line through the stock cooler, then into the aftermarket one, then back to the trans. All instructions with aftermarket coolers say to do this, as well.
 
Originally Posted By: mechtech2
I would never bypass a factory trans cooler that goes in the radiator.
ESPECIALLY in winter!
That is when you need the heating that it provides for a better warm up the most!
Always run the trans line through the stock cooler, then into the aftermarket one, then back to the trans. All instructions with aftermarket coolers say to do this, as well.

MMMMMM....during the winter months my tanny barley reaches 100 degrees on the freeway. City driving maybe 125. If the coolant temps are around 220 or so you should see alittle bit higher temps in the transmission. Mind you these readings are comming out of the transmission. I dont see how running a stock cooler aides in heating up the atf.
 
Originally Posted By: mechtech2
ARB - The stock cooler is in the RADIATOR.
Now do you see how it aids with initial heating up the ATF?

I know its in the radiator (stock cooler)...i think your missing what im saying.
 
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When my Chrysler A-604 grenaded, I had it rebuilt. I completely bypassed the stock cooler as it was full of junk. I have a cooler that has an external bypass you can install inline. The re-builder sold said aftermarket cooler, but did not like the bypass (thermostat) part as he stated that they get gummed up and stop working right. I put in a perma-cool filter inline before the cooler and was going to install the thermostat (bypass of the cooler), but then found out and then confirmed by the re-builder that the A-604 has its own internal bypass. I did not install the thermostat bypass that came with the cooler. It is 20 degrees right now and has been cold off and on here. No problems at all with proper shift points. No problem with completely taking the radiator transmission cooler out of the loop. None, Nada, Zip. Shifts fine in cold and hot weather this past year.

I would have no problem installing the thermostat bypass of the auxiliary cooler if you have an inline filter before it. Should keep it clean and working properly. Also, no problem bypassing the stock transmission radiator cooler with the thermostat for winter.
 
Originally Posted By: SWHeat
When my Chrysler A-604 grenaded, I had it rebuilt. I completely bypassed the stock cooler as it was full of junk. I have a cooler that has an external bypass you can install inline. The re-builder sold said aftermarket cooler, but did not like the bypass (thermostat) part as he stated that they get gummed up and stop working right. I put in a perma-cool filter inline before the cooler and was going to install the thermostat (bypass of the cooler), but then found out and then confirmed by the re-builder that the A-604 has its own internal bypass. I did not install the thermostat bypass that came with the cooler. It is 20 degrees right now and has been cold off and on here. No problems at all with proper shift points. No problem with completely taking the radiator transmission cooler out of the loop. None, Nada, Zip. Shifts fine in cold and hot weather this past year.

I would have no problem installing the thermostat bypass of the auxiliary cooler if you have an inline filter before it. Should keep it clean and working properly. Also, no problem bypassing the stock transmission radiator cooler with the thermostat for winter.

During the winter months its dropped to 18 degrees. I do have a aux cooler with a magnafine filter before it. Do you think with temps in the teens is it worth it getting a bypass cooler or use what i have? I agree with the bypass gumming up idea.
 
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Originally Posted By: ARB1977
Ive been reading were some have experienced radiator coolers bursting causing atf and radiator fluid to be mixed. Guys are having to fork over thousands of dollars for new transmissions and radiators.
DO IT! this happened to me. Had to shell out almost 1000 dollars because of a stupid transmission cooler leak. Make sure you install a good one that is pretty big!
 
If you guys are sold on bypassing the factory transmission cooler in the radiator there is only 1 trans cooler I would get.

It is a B&M trans cooler, it has a built in bypass, this is how it works, when the transmission fluid is thick (cool) the fluid bypasses the cooler.

When the fluid gets hotter it starts to go through the cooler.

This type of cooler is the stacked plate design which is 30% more efficient than the tube and fin type.

If you want to keep junk out of your trans lines install a Magnefine or put a Filtermag magnet on the bottom of your trans pan.
 
Originally Posted By: c3po
If you guys are sold on bypassing the factory transmission cooler in the radiator there is only 1 trans cooler I would get.

It is a B&M trans cooler, it has a built in bypass, this is how it works, when the transmission fluid is thick (cool) the fluid bypasses the cooler.

When the fluid gets hotter it starts to go through the cooler.

This type of cooler is the stacked plate design which is 30% more efficient than the tube and fin type.

If you want to keep junk out of your trans lines install a Magnefine or put a Filtermag magnet on the bottom of your trans pan.


This is what I would use. Early 4 Speed Chrysler transmissions used to go into a partial lock up or lock up mode based on fluid temperature. So if you by passed the radiator it would cause the transmission to always be in partial lockup and cause excessive wear. This was solved on rebuilt transmissions by using an external cooler that had a thermostat that would cause it to bypass the cooler if the fluid was still too cool.

Great sugguestion C3PO
 
Originally Posted By: ARB1977
During the winter months its dropped to 18 degrees. I do have a aux cooler with a magnafine filter before it. Do you think with temps in the teens is it worth it getting a bypass cooler or use what i have? I agree with the bypass gumming up idea.


If you have a good ATF and it is shifting fine, I would not worry about it.

The B&M mentioned is a quality product. I almost went that way, sometimes I wish I had. The one I did put on has better cooling than the B&M, but is not as rugged. I do not think the B&M would overcool due to the fluid dynamics mentioned.
 
When the ambient temp is cold out the radiators don't add any heat. The transmission cooler is on the cold side of the radiator.

I bypassed mine altogether and added a large aux cooler. This keeps the transmission heat out of the radiator in the summer. In the winter even in the coldest of temps (-10F) the transmission fluid will get to about 100F.
 
Originally Posted By: SHOZ
When the ambient temp is cold out the radiators don't add any heat. The transmission cooler is on the cold side of the radiator.

I bypassed mine altogether and added a large aux cooler. This keeps the transmission heat out of the radiator in the summer. In the winter even in the coldest of temps (-10F) the transmission fluid will get to about 100F.

On a cold day here in Texas (18F), what would be a heat wave for some of you guys. The transmission will barely see 100 degree temps.
 
Originally Posted By: ARB1977
Originally Posted By: mechtech2
I would never bypass a factory trans cooler that goes in the radiator.
ESPECIALLY in winter!
That is when you need the heating that it provides for a better warm up the most!
Always run the trans line through the stock cooler, then into the aftermarket one, then back to the trans. All instructions with aftermarket coolers say to do this, as well.

MMMMMM....during the winter months my tanny barley reaches 100 degrees on the freeway. City driving maybe 125. If the coolant temps are around 220 or so you should see alittle bit higher temps in the transmission. Mind you these readings are comming out of the transmission. I dont see how running a stock cooler aides in heating up the atf.


When you have a coolant temp of 200 degrees or so that shows up on your gauge, that temperature is probably taken from your cylinder head.

The trans cooler line is usually on the side of the radiator that is the coolest. I once took some temps with an infrared gun on my Chevrolet El Camino that has a small block chevy and I do not have an external cooler.

I do have a Derale Trans Pan that has cooling tubes on the bottom and I use Amsoil ATF.

Here are the temperatures I recorded in various places after a 30 mile trip 1 summer evening with the temperature outside being about 75 degrees.

1)Cylinder Head ( where temp sensor is mounted) 195 degrees
2) Left side of radiator 180 degrees
3) Right side of radiator 100 degrees
4) Trans Pan 100 degrees
5) Torque Converter 160 degrees

The left side or drivers side of the radiator is where the coolant comes in from the thermostat.

The right side or passenger side is where the coolant has crossed the radiator and where the transmission lines are, since I got a temperature reading of 100 degrees there and not 180 degrees or more it is hard to see how the fluid can be heated up, they are called trans cooler lines not trans heat lines.

When your car is heating up in the winter time, the coolant is heating up in the block, the coolant in your radiator is obviously colder, where your trans cooler lines are is the coldest part of the radiator, so how is the radiator fluid warming up the trans fluid.

If your trans temp gauge is mounted in your trans pan you are not getting the most accurate reading of the fluid's temperature, the torque converter is the hottest place in the transmission I think since the temp there was 60 degrees higher than it was in the pan.

I think the transmission itself will heat the fluid faster than the radiator fluid will. These are just my observations with an infrared gun.
 
Originally Posted By: mechtech2


When you have a coolant temp of 200 degrees or so that shows up on your gauge, that temperature is probably taken from your cylinder head.

The trans cooler line is usually on the side of the radiator that is the coolest. I once took some temps with an infrared gun on my Chevrolet El Camino that has a small block chevy and I do not have an external cooler.

I do have a Derale Trans Pan that has cooling tubes on the bottom and I use Amsoil ATF.

Here are the temperatures I recorded in various places after a 30 mile trip 1 summer evening with the temperature outside being about 75 degrees.

1)Cylinder Head ( where temp sensor is mounted) 195 degrees
2) Left side of radiator 180 degrees
3) Right side of radiator 100 degrees
4) Trans Pan 100 degrees
5) Torque Converter 160 degrees

The left side or drivers side of the radiator is where the coolant comes in from the thermostat.

The right side or passenger side is where the coolant has crossed the radiator and where the transmission lines are, since I got a temperature reading of 100 degrees there and not 180 degrees or more it is hard to see how the fluid can be heated up, they are called trans cooler lines not trans heat lines.

When your car is heating up in the winter time, the coolant is heating up in the block, the coolant in your radiator is obviously colder, where your trans cooler lines are is the coldest part of the radiator, so how is the radiator fluid warming up the trans fluid.

If your trans temp gauge is mounted in your trans pan you are not getting the most accurate reading of the fluid's temperature, the torque converter is the hottest place in the transmission I think since the temp there was 60 degrees higher than it was in the pan.

I think the transmission itself will heat the fluid faster than the radiator fluid will. These are just my observations with an infrared gun.

My temp readings come from the outlet of the transmission...were fluid is at its hottest point before going into the stock cooler.
 
Originally Posted By: ARB1977
Hey fellas,
Im reading some posts on other forums about bypassing the factory radiator transmission cooler with a aux cooler that has a interal bypass for winter months. Ive been reading were some have experienced radiator coolers bursting causing atf and radiator fluid to be mixed. Guys are having to fork over thousands of dollars for new transmissions and radiators.

How wise is this? On my Tacoma im running a TRD style cooler...nothing special after the stock radiator cooler. Ive been doing this for most of my trucks life but im alittle concerned down the road problems could happen. The TRD cooler does not have an internal bypass so i may get rid of that with one that does.

What are your thoughts.


That TRD cooler looks exactly like the B&M Supercooler, so I would think that it has an internal bypass for the fluid when it is cold.

You can go to the B&M site and you can see that it looks just like the TRD Cooler.
 
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