Transmission Fluid Temperature

ramhacker · Aug 15, 2020

Got a 2017 RAM 1500 SLT (Quad/4x4/Pentastar) about a month ago now. Been doing some work to it little by little on the weekends, and one thing I'm paying attention to now is the temps.

Right now it's 80% humidity and in 84 degrees F ambient temperature, I noticed the transmission fluid temp floated around 184-188F just driving the speed limit, no hard accelerations, no towing, and on flat ground. I've read that it should actually be 175F for best life. I have a few questions about this:

1.) Is this a safe/normal range for those conditions on this truck? If not, any suggestions of what to inspect?
2.) When the ATF is about 175, does this mean that the fluid just needs to be replaced more frequently, or that the transmission parts degrade faster? or both?
3.) If I wanted to, would it be useful to upgrade or replace my transmission cooler? I do plan on doing some lighter towing (~4000lbs).

I realize the other possibility is that the sensor is a little inaccurate... I notice that my engine oil temp sensor fluctuates by 2 degrees every few seconds so I expect a little bit of inaccuracy there too...

crash68 · Aug 15, 2020

Your transmission temp is fine, even running upwards of 200°F it's fine. There are lots of these transmissions pulling trailers running 200°F for tens of thousands of miles without any issues. Change it before 100K miles and you should be good. Maybe with old school ATF running above 175°F would degrade the fluid, this doesn't use a standard ATF.
As for the transmission cooler, there is the TMU on the side of the transmission that has the cooler bypass valve. That sends the fluid up to the top couple rows of what also the AC condenser. Unfortunately there's only one company that offers a lower temperature bypass valve and you have to buy one of their high performance transmissions to get it. Some have gone with an extra deep PPE pan but it just slows the fluid temp getting up to temp.
As long as the trans temp doesn't spike above the coolant temp all is well.

Michael Jones · Oct 26, 2020

ramhacker said:
Got a 2017 RAM 1500 SLT (Quad/4x4/Pentastar) about a month ago now. Been doing some work to it little by little on the weekends, and one thing I'm paying attention to now is the temps.

Right now it's 80% humidity and in 84 degrees F ambient temperature, I noticed the transmission fluid temp floated around 184-188F just driving the speed limit, no hard accelerations, no towing, and on flat ground. I've read that it should actually be 175F for best life. I have a few questions about this:

1.) Is this a safe/normal range for those conditions on this truck? If not, any suggestions of what to inspect?
2.) When the ATF is about 175, does this mean that the fluid just needs to be replaced more frequently, or that the transmission parts degrade faster? or both?
3.) If I wanted to, would it be useful to upgrade or replace my transmission cooler? I do plan on doing some lighter towing (~4000lbs).

I realize the other possibility is that the sensor is a little inaccurate... I notice that my engine oil temp sensor fluctuates by 2 degrees every few seconds so I expect a little bit of inaccuracy there too...

Was curious on this as well towards temp. Got my 2018 6.4L Tradesmen 4x4 pretty warm on a few mile up hill mountain road pulling my 19ft rv for hunting. Usually stays around 170. 174 on the highway pulling. But the snails pace on the up hill mountain road with wash board roads made it a challenge. Transmission got up too 204 at one point. But from what I've read she should be good. Only have 13 thousand miles on the truck. Probably change fluid in power train front to back at 30k

PoMansRam · Oct 26, 2020

Yep, my 2017 Ram 1500 pentastar did the same thing.

Got up to ~185F pretty quickly, but even on 90F humid days, with a lot of usage didn't fluctuate much higher than maybe ~190F. Per ZF, the danger zone is 240F+, where fluid degradation speeds up dramatically. On very cold days with the cabin heat blasting, I believe the electronic coolant 3-way valve is directing the majority of the hot coolant to the heater core and not the ATF heater, so you'll notice the transmission temps will not be able to reach 185F.

My 2019 Ram 1500 classic hemi does not have the 3-way coolant valve and it takes the transmission much longer to get to 185F. With temperatures below 50F, it sometimes never gets there. I can drive 20 miles and the trans temp might only be 150F.

62Blazer · Oct 26, 2020

I know what chart you are looking at.....that information has been floating around the internet as long as I can remember, and because of how old it is I'm not sure how realistic it is to today's vehicle. The transmissions and fluids have changed a lot over the years and usually hold up a lot longer and can survive higher temperatures much better than the stuff from the 60s, 70s, and 80s. If you made 100k miles on a car or truck back from the 70's it was considered completely worn out and needed complete rebuild. Nowadays 100k is just considered broken in.

With that said if the trans stays at or below the engine temperature I wouldn't be concerned.

TheEnder · Oct 28, 2020

Michael Jones said:
Was curious on this as well towards temp. Got my 2018 6.4L Tradesmen 4x4 pretty warm on a few mile up hill mountain road pulling my 19ft rv for hunting. Usually stays around 170. 174 on the highway pulling. But the snails pace on the up hill mountain road with wash board roads made it a challenge. Transmission got up too 204 at one point. But from what I've read she should be good. Only have 13 thousand miles on the truck. Probably change fluid in power train front to back at 30k

You have the RFE and 204 is dangerously high for the RFE. 170 is what i’d expect towing, but 204 on these transmissions can lead to catastrophic trans failure. The 8 speed is completely different, they’re capable of running that high because their valve bodies don’t warp and the fluid has a different more heat resistant base oil..

Sent from my iPhone using Tapatalk

Michael Jones · Oct 28, 2020

It started at 174 and ended up at 204 after cresting a steady uphill grade on a mountain road. Was about a 5min, snails pace, pulling my 19ft travel trailer. Once I crested onto flat road I was able to pickup speed to about 20mph. And the transmission started cooling down. She eventually got to 168 about 10min after the pull. Again I was on a mountain road so I really couldn't go to fast without beating up my truck and trailer with kicking up rocks.

TheEnder, what do you suggest? Trade in, private sell it, or change the fluid in the near future?

Anyone else have a opinion on the matter i should consider?

Burla · Oct 28, 2020

Michael Jones said:
Was curious on this as well towards temp. Got my 2018 6.4L Tradesmen 4x4 pretty warm on a few mile up hill mountain road pulling my 19ft rv for hunting. Usually stays around 170. 174 on the highway pulling. But the snails pace on the up hill mountain road with wash board roads made it a challenge. Transmission got up too 204 at one point. But from what I've read she should be good. Only have 13 thousand miles on the truck. Probably change fluid in power train front to back at 30k

The OP has the 8speed, those are normal for that, not for rfe. The fluid will be thin as **** at 204 in rfe, and you are towing as well. You need to bypass your thermo valve bud. But seeing how it dropped, you likely will be ok. But anyhow with the rfe look into upgrades for a long lasting truck.

Burla · Oct 28, 2020

My brother went through three automatics with his Cummins from towing heavy before he went to manual, I wish we would have tried upgrading rfe from stock instead.

Michael Jones · Oct 28, 2020

It stays right at 170 ish, on the interstate doing 60mph, highways 55 to 60mph, byways and city streets. It was just on this 5min pull on a uphill, gravel 4%grade mountain road where she got hot for 5min because I was only able to speed up to 2 to 6mph. Then went back down to 170 ish after 10min once I was back on flat gravel mountain roads driving around 20mph.

Michael Jones · Oct 28, 2020

Sum it all up truck only has 13,*** on it from brand new. Should I just keep trucking or swing by my trusted transmission shop and get a fluid and filter change?

Burla · Oct 28, 2020

If I were you, I would investigate the weaknesses of the rfe, and the beauty of the rfe. I say this because just tossing your hands up and asking if you should change oil means you haven't considered the info being shared with you. The mileage doesn't mean jack rabbit crap with all do respect. The weaknesses are what the weaknesses are. Many rfe's do last long, maybe your will be one of them. But if you feel like addressing it instead of hoping, develop a plan. Don't mean to scare you, like I said maybe yours will last long as is, dunno.

Of first importance, look if you have the thermo valve you should bypass that, before ever thinking of changing fluid. Here is one example, research it. The valve that fca put on your truck, pumps temperature into the truck. The dumbest **** ever built. Then watch that video, good luck partner.

TheEnder · Oct 28, 2020

Michael Jones said:
It started at 174 and ended up at 204 after cresting a steady uphill grade on a mountain road. Was about a 5min, snails pace, pulling my 19ft travel trailer. Once I crested onto flat road I was able to pickup speed to about 20mph. And the transmission started cooling down. She eventually got to 168 about 10min after the pull. Again I was on a mountain road so I really couldn't go to fast without beating up my truck and trailer with kicking up rocks.

TheEnder, what do you suggest? Trade in, private sell it, or change the fluid in the near future?

Anyone else have a opinion on the matter i should consider?

Change the fluid as soon as possible with Redline C+.

This transmission fluid is ATF+4 compatible and has the same base oil as the 8 speed fluid, which is able to withstand higher temperatures. The RFE has WAY too many weaknesses to be at anything over 160 normally.

Sent from my iPhone using Tapatalk

PoMansRam · Oct 28, 2020

Michael Jones said:
Sum it all up truck only has 13,*** on it from brand new. Should I just keep trucking or swing by my trusted transmission shop and get a fluid and filter change?

How much towing have you done in that 13K miles? If it's only a little bit, I'd personally wait till 24K or so for the first pan drop and filter change.

Burla · Oct 28, 2020

It is this easy and will bring down temps.

Burla · Oct 28, 2020

What ender was hinting at, different fluids can operate in heat more then others, however if fca pumps temperature into your trans, that is job one. Line 2 and 5 is redline oil base oils, line one is your random atf4. Thus is why the zf8 transmission uses base oil from line 2, and runs hot. As your additives are used up, notice at what temperature the fluid will fail, right around your 204.

Michael Jones · Oct 28, 2020

PoMansRam said:
How much towing have you done in that 13K miles? If it's only a little bit, I'd personally wait till 24K or so for the first pan drop and filter change.

Truck Only has 2100 miles of towing with only my 19ft rv trailer, of the 13,***. Other than that she rides empty.

Burla · Oct 28, 2020

Michael Jones said:
Truck Only has 2100 miles of towing with only my 19ft rv trailer, of the 13,***. Other than that she rides empty.

That oem thermo valve has gate valve that closes so it bypasses your trans cooler until oil gets hot. Now, those gates fail all the time is fatal nearly 100% of the time when it does, as temps shoot up until the tranny fails. We have guys on ram forum that have lost their tranny simply because they left that oem thermo bypass valve on their truck. Plus, it is very likely you would not have seen 204f on that occasion, because that oem valve artificially raised your temps until it opened. What if when you went on that incline your transmission was at 140f instead of 160f? Who knows right? It is bad tech man.

Michael Jones · Oct 28, 2020

Burla said:
It is this easy and will bring down temps.

Watched the video, definitely straight forward process. I'll definitely look into doing this come next spring when I start camping again and pulling the trailer. At that time I'll probably do a fluid and filter change of a high grade transmission fluid.

Any suggestions on what fluid and filter recommendations?

Burla · Oct 28, 2020

Michael Jones said:
Watched the video, definitely straight forward process. I'll definitely look into doing this come next spring when I start camping again and pulling the trailer. At that time I'll probably do a fluid and filter change of a high grade transmission fluid.

Any suggestions on what fluid and filter recommendations?

You need the rfe metal thread upgrade and you cal go with synthetic filters here is the thread. That is the spin on, now the oem sump filter is imo the best just replace with mopar sump filter. For a hot transmission you should look at ester based, which is redline c+ (both ester and pao) which is what I use in my rfe. I did a drop pan and filter change, it took 8 quarts, most people say it took 7 who have done the same.

The one with the hex are the best threads, a lot of guys don't use other upgraded ones over this one.

Transmission Fluid Temperature

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