Trans temp high limit - Page 2 - Dodge Cummins Diesel Forum
3rd Gen. Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission Ect...NO ADVERTISING

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post #13 of 82 (permalink) Old 04-20-2019, 09:14 AM
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Originally Posted by ChaotusCummins083500 View Post
Ya I've been told that too I just figure it runs off the ECU if the ECU sensed Trans problem I'd probably get a lift plus it's a chrysler product we all know how they are about their lights which if I were to get a trans code in the tuner or a trans light even I'd treat it as if my truck was dying and get it checked out asap just good to know the Trans fluids of today have much better tolerances, plus if I were to get and slipping or hear and noises I'd freak out pretty much the same so all is well hope for the best right but I'm gonna change the fluid soon and I'll get a better idea at that point

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The 68RFE is a completely different setup than the OP's 48RE.


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post #14 of 82 (permalink) Old 04-20-2019, 06:33 PM Thread Starter
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Verify that your monitor is reading correctly before getting too worked up. My experience has shown the digital displays that read out info from the data stream are horribly inaccurate. They are typically anywhere from 20-30 degrees off.
Is it the gauge or the data stream (OEM sensor) that is off? Cerberusiam suggests that 240 is where the ECU/TCU intervenes (sets light and modifies shift patterns). Will I see 240 on my gauge when that happens or is my gauge interpreting the data stream differently than the ECU/TCU? I assume they're getting their info from the same sensor.

What is the simplest (least invasive/expensive) way to add cooling to the transmission? I have already purchased and installed the thermostat delete kit.

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post #15 of 82 (permalink) Old 04-20-2019, 07:50 PM
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Originally Posted by Dynamic View Post
Verify that your monitor is reading correctly before getting too worked up. My experience has shown the digital displays that read out info from the data stream are horribly inaccurate. They are typically anywhere from 20-30 degrees off.
Not to mention the choice of sender location can produce wildly different temps. You can see equally large swings just moving around the side of the transmission pan of a fully warmed up truck with an IR thermometer.

I don't know where the OEM sender is, but you have to consider they factored the sender location into the 260* threshold.

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post #16 of 82 (permalink) Old 04-20-2019, 09:18 PM
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OBD port info is coming form the sensor in the pan. Whether or not your choice of gauge reads the same as the TCM is another question. It has to convert a voltage reading to a temp so there is not telling if the gauge does it the same as the TCM. The OE sensors typically read high because the data is interpolated from the sensor and the sensors are notorious for inaccuracies. This is the same senor that is responsible for reading back gov pressure and we all know how good it is.

IR gun is totally useless, all it will tell you is heat soak in the case and that is frequently far form actual fluid temp. Useful for temp comparisons from divorced components like brakes but that is about it.

Temp in the pan always lags actual heat generated in the trans because it is reading a mix of sump and cooler return fluid. By the time it is hot everything is hot. If you want a gauge to actually drive by then the probe needs to go in the front cooler output line. That gives you an idea how hard the TC is working and will be the hottest temps. Whne it hits 240 the trans will lagging way behind and you can adjust gears and driving to bring it down instead of wondering what is going on.

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post #17 of 82 (permalink) Old 04-20-2019, 09:41 PM
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Originally Posted by cerberusiam View Post
OBD port info is coming form the sensor in the pan. Whether or not your choice of gauge reads the same as the TCM is another question. It has to convert a voltage reading to a temp so there is not telling if the gauge does it the same as the TCM. The OE sensors typically read high because the data is interpolated from the sensor and the sensors are notorious for inaccuracies. This is the same senor that is responsible for reading back gov pressure and we all know how good it is.

IR gun is totally useless, all it will tell you is heat soak in the case and that is frequently far form actual fluid temp. Useful for temp comparisons from divorced components like brakes but that is about it.

Temp in the pan always lags actual heat generated in the trans because it is reading a mix of sump and cooler return fluid. By the time it is hot everything is hot. If you want a gauge to actually drive by then the probe needs to go in the front cooler output line. That gives you an idea how hard the TC is working and will be the hottest temps. Whne it hits 240 the trans will lagging way behind and you can adjust gears and driving to bring it down instead of wondering what is going on.
This is exactly what I meant about temp variation and trusting the factory sender. When they say 260* - at this spot- is bad? You're there.

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post #18 of 82 (permalink) Old 04-20-2019, 10:05 PM
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Originally Posted by njmurvin View Post
Is it the gauge or the data stream (OEM sensor) that is off? Cerberusiam suggests that 240 is where the ECU/TCU intervenes (sets light and modifies shift patterns). Will I see 240 on my gauge when that happens or is my gauge interpreting the data stream differently than the ECU/TCU? I assume they're getting their info from the same sensor.

What is the simplest (least invasive/expensive) way to add cooling to the transmission? I have already purchased and installed the thermostat delete kit.
Add a Gorend aluminum transmission pan with extra capacity, drain plug and temperature probe port.

Add Edge temperature probe and interface. Monitoring the transmission pan will avoid the constant temperature swings and still allow enough time to pull over and cool things down. You should see 150F normal and 285F max for short duration on a steep hill at maximum load. Damage occurs at 300F. Maximum fluid level checking temperature is 190-200F because of thermal expansion. I never see more than 185F towing 5000lbs in the mountains using a Ford mechanical fan controller instead of the troublesome stock ECU driven fan controller.

Make sure your water temperatures are normal and you can hear the fan when things get warm.

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post #19 of 82 (permalink) Old 04-21-2019, 08:48 AM
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njmurvin

No mention in your signature of any 48RE upgrades. Can't imagine you're towing 20k+ GCVW 5er with stock 48RE. fill us in, HD aftermarket torque converter? built towing valve body? HD clutch/steels packs?

A HD built torque converter specifically for towing will reduce the tremendous heat produced in a stock OEM factory TC with far more efficient turbine/stator combo that doesn't turn all that Cummins torque into heat and smoked ATF, a lockup clutch that does NOT slip under load >less frictional heat.

Spot ATF temps in a poorly built or running auto tranny can easily hit 400d F. in shoddy cheap stock OEM TCs, in clutch packs, pump gear teeth, etc.

Clutch packs that do not slip and produce frictional heat.
Towing VB that has much higher line pressures and far better ATF flow control for smooth efficient shifts.
Remember, Mopar went cheap on the 48RE so they had to limit the stock torque output via shortcuts in the tranny and powertrain control software.

If you already have an aftermarket tow build 48RE, then add a frame mounted fan cooled plate fin ATF cooler in series with the in front of engine mounted stock unit. Bypass the ATF>water cooler mounted on the driver side of block> they leak and kill $5000 trannies.
Install an auto thermostat switch for new cooler and a manual switch that you can kick on before a high long pass such as the Rockies. Use high quality lines and fittings. Major leak from blow line or loss of ATF by fittings will ruin a long trip in remote areas.
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^ what cerb said above about add on ATF temp sensor location.
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post #20 of 82 (permalink) Old 04-21-2019, 11:40 AM
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Like said above ie my smarty touch reads from the internal sensor and is usually 20 deg hotter than the pan temp probe.

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post #21 of 82 (permalink) Old 04-21-2019, 11:48 AM
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The best way I found to combat an early demise from excessive trans temp, and I have killed a brand new trans in one trip before...is with better cooling. i have two Derale 25 row coolers mounted right where the factory cooler was, with no thermostat and then I have a BD cooler with a thermostat and fan under the bed so if temps ever do get over 180 the fan kicks on and lowers it to 160 and it will even kick on after shut down to kool it while you're parked. I have a pic somewhere with my intercooler off to show how I mounted them. Pretty Kool since I live in the desert i have no fear of long idling and slow crawling up hills and on the trail where temps can really get HOT!
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03 Dodge SHO CCLB Dually Carli/Thuren Argon filled Shocks, radius arms, SRW 4 link Conversion, 17"methods, 42" Goodyear MTR Kevlar Tires / 6 in a row ready to tow!

Last edited by Gator1; 04-21-2019 at 12:22 PM.
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post #22 of 82 (permalink) Old 04-21-2019, 12:29 PM
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I dunno, my trans shifts the best the cooler it is before it looses it's viscosity. Some like changing smoked bands, and clutch packs I guess.
If you have shift quality changes in 40 degrees of fluid temp you have issues with the trans build. Shift quality that relies on cold fluid to work correctly has leaks and\or incorrectly setup clutch packs. That WILL end up in smoked clutches eventually.

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Originally Posted by micromike View Post
Monitoring the transmission pan will avoid the constant temperature swings and still allow enough time to pull over and cool things down.
That is another idea that makes ZERO sense when logic is actually applied. One should never have to "pull over and let it cool down", that is operator error and lack of understanding what is going on. A trans temp gauge in the right spot negates all of that. Gauge that reads pan temp is bling, pure and simple. SMH!!!

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post #23 of 82 (permalink) Old 04-21-2019, 12:46 PM
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[QUOTE=cerberusiam;28961789]If you have shift quality changes in 40 degrees of fluid temp you have issues with the trans build.



More like 100+ deg changes.... and not a bad thing.... just something I notice.

03 Dodge SHO CCLB Dually Carli/Thuren Argon filled Shocks, radius arms, SRW 4 link Conversion, 17"methods, 42" Goodyear MTR Kevlar Tires / 6 in a row ready to tow!

Last edited by Gator1; 04-21-2019 at 12:49 PM.
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post #24 of 82 (permalink) Old 04-21-2019, 01:29 PM Thread Starter
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njmurvin

No mention in your signature of any 48RE upgrades. Can't imagine you're towing 20k+ GCVW 5er with stock 48RE.
Actually, I am. 12K is the GVWR of my trailer. I'm sure it's a little less, but close. I've had this trailer for 3 years. The previous one was 10K. I have 95K on the truck which I've owned since new. I have done drain/fill and filter every 15K since new. I've never reached the temp where lights come on and hope I never will. I don't care if my gauge just reads 20 deg high all the time if I can depend on that and adjust my actions based on it. I'm not opposed to installing an Edge temp probe in another location if that gives me a more reliable red-line. I recently started getting P0483 (twice now) which I interpret as meaning my fan clutch is failing. Does the trans temp engage the fan if the ECT isn't high enough to do so? Regardless, I plan to order an OEM fan clutch and install before my next trip in June.

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