Transmission cooler through radiator or not?

Ataylor

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I have a 1987 F350 with a C6. I going to put a larger aux. transmission cooler in place of the stock 2 pass cooler. I wondering if I should keep the lines running through the radiator trans. cooler or just bypass it. I have heard that it helps the transmission warm up faster on cold days, but I would think that when it is 105 F. outside, and I'm towing, the coolant will be over 200 F which would heat up the trans. fluid more.

I had a guy at a local tranny shop tell me to definately keep the radiator trans cooler in the loop, but he really didn't say why it was so important.

What is your opinion?

Thanks for your time,

Archie Taylor
 

trackspeeder

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Keep it. It dose make a difference in cooling.

The cooler in the radiator doesn't heat the tranny fluid. It will always cool the fluid.
 

sootman73

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both tranny guys i had work done with told me to get it out of the loop! the radiator coolers have corners and not tubes. they can clog. its what happened to my first tranny. ended up killing the thing. so i took a AC condenser and use that for my cooler. never goes above 160 degrees F.
 

franklin2

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The instructions with the aux coolers tell you to keep the radiator section in the loop. Since they designed the thing, I always follow what they say. There is also a certain line you have to use from the tranny and it has to go to the radiator first. They tell you how to pick the right line in the instructions also.
 

LCAM-01XA

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On a hot day the coolant will be around 200F yes, but that's the one in the top of the engine about to be discharged into the radiator. The coolant returning from the radiator into the engine has much much lower temperature, it then gets heated to 200F again as it runs through the engine. This is why transmission coolers are always in the cold tank of the radiator, so they never see the real hot coolant being pumped out of the engine.

Now, whether to bypass the factory cooler or not - keep in mind if you go with a big air-cooler the only thing moving air through it when you're idling in a gridlock is the engine fan, however since diesels don't make much heat while idling and the radiators of these trucks are already quite big the fan won't move much air since it don't need to for engine cooling purposes. The transmission however keeps producing heat even when idling, so all of sudden it may turn out that the little air pulled by the engine fan is more than enough to keep the engine happy, but it's not enough for the transmission, and unless you have an external electric fan on the trans cooler there ain't nothing you can do about it other than maybe kicking in the high idle (if so equipped) to spin the engine faster and make more heat so the fan locks up more and starts pulling more air. This issue will be even more apparent in hot summer days, and this is where the factory liquid cooler really shines, since it don't care for airflow but rather just coolant temperature. The only safe way to run just air cooling is what I'm doing - A/C condenser as a cooler, and fan blowing full speed all the time.
 

SparkandFire

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I agree w/ M.L.S.C., on the hot, bumper-to-bumper days, your radiator cooler will be helping out far more than you realize.

not to mention that a liquid to liquid heat exchanger is quite a bit more efficient than an air to liquid exchanger. The coolant at the bottom tank of the radiator is quite cool. I've always plumbed the radiator cooler in first, then the aux cooler, then back to the trans...

I saved a crappy mazda 626 tranny this way, nearly melted down once and I installed the aux cooler, put another 40,000 miles on that beast till I sold it!

Was kinda funny to see a 30,000 GVW RV tranny cooler zip tied to the front of a mazda 626, anyhow! :sly
 

Ataylor

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Thanks for all the replies!

Thanks for everyone's input on keeping the radiator transmission cooler. Sounds like keeping it in the loop is the best plan.

Archie Taylor
 

LCAM-01XA

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Well the pump is still running and moving the fluid though the passages. The converter's turbine just freewheeling for the most part, yes, this will reduce heat generation quite a bit - however do you really wanna risk it?
 

Fozz

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I could have sworn that I read somewhere that there is a thermostat/valve/type thing in the E4OD that doesn't even open to allow hydralic fluid flow (cooling) until it reached a certain temp. So, taking the rad cooler out of the loop would work against the E4ODs temp controling feature. But, I just remembered that you can disconnect the return line and pump out the fluid when changing the fluid, so that would contradict my thinking, maybe I had too many beers when I thought I read that.

Anyway, put a big aux cooler on after the rad and you'll be fine. I put a 24k gvw cooler on mine and it does very well, even when towing my 5r. They're only $50 or so online and come with hose and fittings.
 

87crewdually

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I could have sworn that I read somewhere that there is a thermostat/valve/type thing in the E4OD that doesn't even open to allow hydralic fluid flow (cooling) until it reached a certain temp. So, taking the rad cooler out of the loop would work against the E4ODs temp controling feature. But, I just remembered that you can disconnect the return line and pump out the fluid when changing the fluid, so that would contradict my thinking, maybe I had too many beers when I thought I read that.

Anyway, put a big aux cooler on after the rad and you'll be fine. I put a 24k gvw cooler on mine and it does very well, even when towing my 5r. They're only $50 or so online and come with hose and fittings.

The 4r100 has the cooler by-pass line that goes from the two ports of the tranny. All the line contains is a little valve with a spring that when the atf gets warm it allows it to open the valve and the fluid goes through the cooler(s).
 

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