Transmission fluid heater/cooler? - Dodge Cummins Diesel Forum
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post #1 of 12 (permalink) Old 06-10-2019, 01:07 AM Thread Starter
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Transmission fluid heater/cooler?

When hauling heavy loads, my transmission seems to overheat quicker than it should. I have a stock tranny cooler up front, and a very large extra cooler also. The cooler lines also pass fluid through a heat exchanger next to the block on the right side of the engine. Seems to me if hauling a load, the hot engine is just going to add extra heat to the tranny through that heat exchanger. Has anyone bypassed that heat exchanger? Obviously, you need it in cold weather, but what about in hot weather?

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post #2 of 12 (permalink) Old 06-10-2019, 10:08 AM
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Even in hot weather the Oil to Coolant heat exchanger is extremely efficient at removing heat straight off the converter WAY more efficient than oil to air flow coolers .

That being said your issue is probl the up front oem cooler thermostat or the check ball in the rubber line towards the front .

Where are you getting the temp readings from , the temp reading that uses oem data thru an EDGE CTS or the like is nortoriusly high and not all that accurate . Best bet is a temp probe in the pan IMO

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post #3 of 12 (permalink) Old 06-10-2019, 10:11 AM
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And YES many have deleted the heat exchanger , for several reasons . One is it is somewhat prone to burst internally and ruin the auto trans with anti freeze .

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post #4 of 12 (permalink) Old 06-10-2019, 11:07 AM
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I've never seen one legit instance of the cooler failing and ruining the trans. The trans lube circuit (cooling circuit in lay terms) pressure is higher than the engine cooling system. When they fail, and we don't hear about it that often, an oil slick of ATF develops in the overflow tank.

The coolant lines going to the heat ex attach to the lower radiator hose inlet (~ambient temp) and right off the water pump discharge volute (warmer than ambient but not 190F either, coolant has only passed through the pump, not the entire block and head). It's as important for cooling in all temps, and fluid shear in an unlocked TC is capable of heating the fluid much more than an engine running warm.

There is no thermostat in the stock oil-air cooler. If the check ball was restricting flow to an extent trans temps were climbing "too fast", he'd have wrecked the transmission from lube starvation before now.

I second the questionable gauge/sensor. My factory one read so low the PCM wouldn't allow lockup/OD in temps below 60f. Replaced it with a new one, same issue. Finally tricked it with a resistor and installed an aftermarket gauge.

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post #5 of 12 (permalink) Old 06-10-2019, 05:32 PM
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I wonder how often the heat exchangers actually fail.

I was doing research when gathering parts for my trans rebuild I ran across a bunch of threads talking about them failing and dumping coolant into the trans ruining it. I bypassed mine at that time and added another air to air cooler. My trans will still get a bit toasty once in a while and I'm thinking of going back to the heat exchanger setup.

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post #6 of 12 (permalink) Old 06-10-2019, 05:58 PM
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Ususally they rust out and leak externaly. According the previous owner, the orignal unit on mine rusted mine and leaked.

Im currently running tonys old heat exchanger.

Before I could hit 270* very quickly hot line temp. Now i will just barely hit 230 pulling a long hill loaded out of lock up.

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post #7 of 12 (permalink) Old 06-10-2019, 08:24 PM
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A buddy of mine had one fail on his 2003 and it took the trans with it. I pulled mine when I went compounds and put a Derale 15870 under the bed and that thing would cool it down real quick.

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post #8 of 12 (permalink) Old 06-10-2019, 09:47 PM
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It should be noted because I gave incorrect info , some of the info I gave was for 3rd gens . My bad.

The 2nd gens have the steel tank style heat exchanger . And yes they go bad ( just less freq than 3rd gen ) . Also there is no thermostat on that lil undersized thing they call a cooler .
3rd gens have the alum stacked plate heat exchanger / converter cooler , and they ARE occasionally very expensive troublesome units. The 3rd gens have a thermostat / bypass in the up front oil to air cooler , that can be troublesome as well.

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post #9 of 12 (permalink) Old 06-11-2019, 04:10 PM
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I have a mishimoto trans cooler on mine that's the factory replacement I remove the check ball I still have heat exchanger and a deep pan just normal driving my temp stays under 150 highest temp I seen was 180 truck and trailer gross out at 20000lbs i was down in 2nd gear lock up pulling a really steep hill. My exchanger has 461000 miles on it.

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post #10 of 12 (permalink) Old 06-12-2019, 12:03 AM
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Quote:
Originally Posted by pa coal roller View Post
I have a mishimoto trans cooler on mine that's the factory replacement I remove the check ball I still have heat exchanger and a deep pan just normal driving my temp stays under 150 highest temp I seen was 180 truck and trailer gross out at 20000lbs i was down in 2nd gear lock up pulling a really steep hill. My exchanger has 461000 miles on it.
What does it do out of lock up.

Daily driver/ workhorse: 1994 2500SLT 4x4 Auto. Hewitt EGT, Boost, Trans gauges, Under hood Mech FP gauge, Trident fuel lines, Tork Tek OFV, Mag-Hytec DD Transmission Pan, Ford manual hub conversion, Diamond eye 4" turbo back, 37337 Upgrade. 260K

98 2500slt 4x4 ECLB moldy G56, south bend clutch 3rd gen trac bar , boxed control arms, billet tappet cover w/ dual breathers trident fuel lines, Tork Tek OFV, 4' stainless side dump with muffler 240k
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post #11 of 12 (permalink) Old 06-12-2019, 10:44 AM
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I'm entertaining the idea of hooking that badboy back up. Maybe I should take it off and inspect it before I drop the money for the coolant & trans lines.

1997 ECLB - 5" Diamond Eye straight pipe - ISSpro Trans temp/EGT/Boost - AFC Live - boost elbow - 191s - Built trans - BHAF - ARP 425s - PSC SG852 - 315/75/16
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post #12 of 12 (permalink) Old 06-12-2019, 01:18 PM
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I am not sure what it does out of lockup When towing I try to keep the converter lockup. It's hard on them towing with out converter lockup. The only reason my temp even got that high was because my egts were getting out of control my engine temp was 220 I had to pull over at the top because the insulation on the firewall was smoking.

2012 cc dually 6speed, mini max, cooler delete, h&s intake horn, boost tube,5ich pipe,gdp big line kit Amsoil dealer since 2006
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