Transmission temperature - JeepForum.com

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post #1 of 29 Old 04-06-2015, 11:27 AM Thread Starter
maureen58
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Transmission temperature

I have a 2015 Grand Cherokee Limited with the 8 speed automatic. My 2012 Laredo with the 5 speed trans would run about 170 degrees. How hot does the new ZF trans run? I saw mine at 200+ the other day, about the same as the engine temp.

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post #2 of 29 Old 04-06-2015, 12:59 PM
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I had a 2014 for 2 years and just traded it for a 2015 a week ago. Both are the 3.6/8 speed and I noticed the trans runs at about the same temp as the motor. 185 to 205, I've seen mine get as hot as 220 a few times in low speed/steep grade situations.

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post #3 of 29 Old 04-06-2015, 02:15 PM
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I would say that's one of the not-so-great parts of the new 8 speed - no transmission cooler, and a large number of gears makes for a hot transmission. Every 20C you raise your transmission temps, you cut the lifespan of the "life-time" transmission fluid in half. For us, that means that those 220+ temps are bad, bad, bad, and you should have your transmission serviced far more often than chrysler would like you to. Here's a great video from a guy with a Dodge Ram with the same transmission

https://www.youtube.com/watch?v=WI6D1xUOEKQ
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post #4 of 29 Old 04-06-2015, 02:39 PM
wyat72
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Remember this trans uses newer more advanced fluids that can take higher Temps.

It is far from atf4 that starts breaking down at 200 degrees.

2011 Grand Cherokee Laredo X, Pentastar, Qudra Trac I.
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post #5 of 29 Old 04-06-2015, 03:07 PM
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Quote:
Originally Posted by wyat72 View Post
Remember this trans uses newer more advanced fluids that can take higher Temps.

It is far from atf4 that starts breaking down at 200 degrees.
Got a source for that? As much as I love some of the rumors the car industry can spread, I highly doubt that we have magic transmission fluid.
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post #6 of 29 Old 04-06-2015, 03:58 PM
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Quote:
Originally Posted by Ampt View Post
Got a source for that? As much as I love some of the rumors the car industry can spread, I highly doubt that we have magic transmission fluid.
I have wanted an answer to this q myself so I sent it to ZF Tech Support, who knows, just might get an answer....I'll post what they say...

FWIW, the flash point is 435 deg F (not an initial breakdown temp) for the Amsoil ATL (L is correct) that specifically meets, and exceeds, the ZF 8&9 Speed ATF spec.
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post #7 of 29 Old 04-06-2015, 04:19 PM
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Yeah... no one anywhere has been able to get a max operating temp on the transmission or the fluid, despite it being used in everything from BMW's to Ram trucks... It just seems highly odd and concerning that no one knows what the safe temp range is on this thing, especially when the fill is "for life".

As for the flash point, that's an OK starting point, but knowing when the material will combust isn't really indicative of when we can expect it to break down unfortunately. After seeing the video I posted above, I plan on dropping the transmission pan at 40-50k and seeing what I've got, and that will tell me what I can expect in the future.
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post #8 of 29 Old 04-06-2015, 05:13 PM
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http://www.zf.com/corporate/en_de/pr...il_change.html

This is the fluid that zf uses in its transmissions. If it reaches 230 regularly change every 120,000km. 220f every 180,000km. 210f every 240,000km.

This trans can operate at higher temps because its fluid is engineered to operate at those Temps. How is it hard to believe that a state of the art trans can operate at higher temps then trans developed 20 years ago.

Google Chrysler's thermal management. Uses engine temps to get the trans to its optimal efficiency range. 190s to 200s.

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post #9 of 29 Old 04-06-2015, 05:19 PM
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Originally Posted by wyat72 View Post
http://www.zf.com/corporate/en_de/pr...il_change.html

This is the fluid that zf uses in its transmissions. If it reaches 230 regularly change every 120,000km. 220f every 180,000km. 210f every 240,000km.

This trans can operate at higher temps because its fluid is engineered to operate at those Temps. How is it hard to believe that a state of the art trans can operate at higher temps then trans developed 20 years ago.

Google Chrysler's thermal management. Uses engine temps to get the trans to its optimal efficiency range. 190s to 200s.
Our transmissions use neither the ZF-Ecofluid M or the ZF-Ecofluid A Life so I don't think that either of those fluid's operating temps pertain to our Jeeps. Our vehicles the ZF-Lifeguardfluid 8. It's hard to believe because there's no proof! No numbers, no zip, no nada! I can easily imagine pigs flying or hell freezing over, but that doesn't make them any more real, does it?

edit: also, looking at your numbers, you've only proven one of my points, an extra 20 degrees cuts the life of the transmission fluid in HALF! Not sure I trust the "life-fill" qualities of a fluid that could vary in life anywhere from 1-8x it's lifespan over 60F
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post #10 of 29 Old 04-06-2015, 05:35 PM
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I was going to edit my post but you beat me to it.

I thought I clicked on a link about zf 8hp fluid, but re reading the Web page I just noticed it was just a zf general fluid. My bad.

I'm not saying I trust fill for life either, but I am saying that I believe this trans can operate at higher temps then the "average" trans, because the fluid can handle it.

2011 Grand Cherokee Laredo X, Pentastar, Qudra Trac I.
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post #11 of 29 Old 04-06-2015, 05:38 PM
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I was going to edit my post but you beat me to it.

I thought I clicked on a link about zf 8hp fluid, but re reading the Web page I just noticed it was just a zf general fluid. My bad.

I'm not saying I trust fill for life either, but I am saying that I believe this trans can operate at higher temps then the "average" trans, because the fluid can handle it.
Haha, they say I've got the fastest enter key in the west. But in reality, yeah, I think it can handle more heat than a transmission from 1995. The big question is how *much* more can it handle? I've got a 3.0 EcoDiesel on an Overland, and traveling around in 0-25F throughout the winter, I saw temps at 212F regularly. No towing, no nothing. Me, the jeep, and all the fluids needed to make it run. How hot will it be in 100F, towing a 5000lb trailer? Everything within specs, but without some sort of active cooling (which it doesn't have) how can I have ANY faith that this thing isn't going to overheat and absolutely fry the transmission fluid?
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post #12 of 29 Old 04-06-2015, 05:43 PM
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https://www.google.com/url?sa=t&sour...9t904Vue1E2HvA

Here is a link to a small pdf, stating that the fluid can operate at higher temps and has heat resistance properties.

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post #13 of 29 Old 04-06-2015, 07:30 PM
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The ZF 8 speed is designed to run hotter:

http://courses.chrysleracademy.com/M.../Reference.pdf

"The 8HP transmission family is such an efficient transmission there is a need for an auxiliary heater to keep the transmission oil at the proper temperature, about 80C (176F).
Engine coolant is carried back to a heat exchanger via coolant pipes. In this illustration, the hoses and pipes have been color-coded to show the hot and cold portions of the system (Fig. 18). The coolant pipes and heat exchanger are serviceable separately."

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post #14 of 29 Old 04-06-2015, 08:30 PM
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Quote:
Originally Posted by wyat72 View Post
http://www.google.com/url?sa=t&sourc...9t904Vue1E2HvA

Here is a link to a small pdf, stating that the fluid can operate at higher temps and has heat resistance properties.
Those are all material properties of the fluid, yes, but they are more about flamability and storage rather than use. The Flash point and specific gravity are great for handling the fluid, but tell us nothing about when the fluid starts to break down and become a solvent rather than a lubricant. I think you're going to be surprised to find that none of the things you find will help answer those questions

Quote:
Originally Posted by 2014RedHemiGC View Post
The ZF 8 speed is designed to run hotter:

http://courses.chrysleracademy.com/M.../Reference.pdf

"The 8HP transmission family is such an efficient transmission there is a need for an auxiliary heater to keep the transmission oil at the proper temperature, about 80C (176F).
Engine coolant is carried back to a heat exchanger via coolant pipes. In this illustration, the hoses and pipes have been color-coded to show the hot and cold portions of the system (Fig. 18). The coolant pipes and heat exchanger are serviceable separately."
Now this is interesting, but I'm concerned that the modifications made to accommodate the RAM are going to knock what we see here out of line with what we see in our Jeeps. For one, I don't think we have the hydraulic impulse storage, due to that being a part of the start/stop system for fuel efficiency in the RAM. Secondly, owning an EcoDiesel, my temps may be higher than what are on the Hemi or V6, meaning that my engine coolant probably also runs hotter. If that's true, the heat exchanger may actually be rising the temps too high. Additionally, we need to figure out if the heat exchanger can work backwards, that is, can it be used to cool the transmission too? That would be a game changer in my perspective, as everything I've read says that the transmission has no cooling beyond what it loses passively!
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post #15 of 29 Old 04-06-2015, 08:47 PM
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Good point, however, the ambient should always be cooler than the fluid temperature (unless you're driving in a volcano). Therefore, it does cool it down (like your radiator does for the engine coolant).

Quote:
Originally Posted by Ampt View Post
Additionally, we need to figure out if the heat exchanger can work backwards, that is, can it be used to cool the transmission too? That would be a game changer in my perspective, as everything I've read says that the transmission has no cooling beyond what it loses passively!
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