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High Road Travelers · 12-07-2020, 10:33 PM

I just installed a ScanGaugeII in my 2018 F53 with the six speed transmission, because I was low in transmission fluid and the shop said they thought it blew out the vent on top of the transmission because it probably got hot. I watch the dash gauges extremely close and neither the engine temp nor the transmission temp gauges have ever wavered off dead center; even going up and down mountain passes in Colorado.
So I am going to monitor the engine and transmission temperatures closely. My problem is I can't find out what the appropriate safe temp range is for either. I have seen varying suggestions on forums and google searches ranging from over 200 is hot, over 220 is hot and a Ford service manager said over 250 degrees is hot. From what I have gathered the engine and transmission temps should run about the same temp.
The transmission uses Mercon LV ATF.
My question - What is the normal operating temp for engine and transmission, and at what temp should I pull over or be really concerned?
Thanks,

akeagle · 12-07-2020, 10:43 PM

Great question. I also look forward to the answer(s).

GypsyR · 12-08-2020, 08:38 AM

If you Google something like "optimal operating temperature of an internal combustion engine" you get 195-220F. (I use Google as an example because I'm just some guy, right?) Automatic transmissions are in fact designed to operate optimally at around the same temperatures. Except according to charts made by people who sell transmission coolers. Their logic is that cooler is better. Apparently to the point that if you cooled your transmission to absolute zero it would last almost indefinitely. Or something. Silly.

Engines and transmissions have a minimum temperature they must achieve to boil off moisture that condenses in them due to the heat cycling of normal usage. In engines running too cool causes a nasty black sludge which people tend to blame on engine oil. In transmissions it causes internal rust. You wouldn't think an aluminum box literally flooded with fluid could rust internally but they do. I've seen valve body plates pitted tot the point of having holes in them. On some GM trucks you can sometimes pull out the transmission dipstick to find you only have a small nub on the handle. The rest having rusted away in the tube.

Taffeys · 12-08-2020, 09:35 AM

Quote:

Originally Posted by GypsyR

If you Google something like "optimal operating temperature of an internal combustion engine" you get 195-220F. (I use Google as an example because I'm just some guy, right?) Automatic transmissions are in fact designed to operate optimally at around the same temperatures.

If you search (I use a private search engine like https://www.startpage.com/ ) for something like "optimal operating temperature of an automatic transmission" you get "around 175 degrees" and "between 175 and 225 degrees". BTW, water boils at around 212 degrees F at sea level which is where I live.

Taffeys · 12-08-2020, 11:18 AM

Quote:

Originally Posted by wog099

My question - What is the normal operating temp for engine and transmission, and at what temp should I pull over or be really concerned?
Thanks,

My 2-valve V-10 engine runs at 190 to 192 degrees almost all the time, I’ve only seen it go to 195 on a few occasions. I have the 5R110 5-speed with Tow/Haul and the transmission temperature usually runs between 190 and 210 and has never been higher. I have been told this transmission is rated at 250 max. But I have heard/read Ford actually says something like 270. The engine and transmission cooling systems on my MH are huge and on your MH are probably even bigger and perform better. I would be concerned about the transmission at 220 and pull over at 250 with my MH.

twinboat · 12-08-2020, 11:30 AM

According to My Scan Gauge II, my 2017 E450 Axis, engine coolant runs between 195 and 205° degrees.

It may climb to 215 on hills, in hot weather.

I don't monitor the trans temps, because when I did, it basicly mirrored the coolant temps.

GypsyR · 12-08-2020, 12:29 PM

Mirroring the ideal range of engine coolant temperatures is about perfect.

Modern transmission fluids (Mercon V, LV, SP, etc) are synthetic oils and much more tolerant of higher temperatures than the older Dexron III/Mercon from the 1990's and earlier.

Last I checked water doesn't need to reach boiling temperature to to evaporate. Higher heat speeds and encourages the process though.

Later model Dodge truck transmissions are coming with little internal electric heaters for the transmission fluid. For two main reasons (I am told). First is fuel economy and performance suffer when the fluid is cold. Secondly, to help burn off moisture.

move on · 12-08-2020, 02:22 PM

Oil that is too cold doesn't flow well and may not get to where it's needed. Most engine bearing wear, for example, takes place when the oil temperature and viscosity are too low. Every machine element has its ideal oil viscosity range and that means 1) selecting the proper oil and 2) controlling its minimum and maximum temperature.

Sweetbriar · 12-08-2020, 03:09 PM

I normally see my 5 speed temp hanging around 165 to 170 deg on my Scan Gauge. Long east coast summer hill climbs I might see 175 or so. I would start getting concerned at 190 deg as after 10 years and 60K miles I've never seen it that high so if the temp hits that mark something must be wrong. I know at 220 you start hitting the danger zone and bad things happening if you stay that high for too long.

TeJay · 12-08-2020, 08:53 PM

After 43,000 miles using a scan gauge with trips to FL and ME in the summer the trans fluid temps hover around 175 to maybe 190 on a steep climb.

The coolant temps stay between 190 to maybe 205 but I don't ever recall any temps above 205. I have never seen the trans and coolant temps mirrored.

mr.tommy · 12-09-2020, 08:04 AM

Quote:

Originally Posted by TeJay

After 43,000 miles using a scan gauge with trips to FL and ME in the summer the trans fluid temps hover around 175 to maybe 190 on a steep climb.

The coolant temps stay between 190 to maybe 205 but I don't ever recall any temps above 205. I have never seen the trans and coolant temps mirrored.

I've never seen the trans and coolant temps mirrored either on our ScanGauge II. We have a 2012, V10, 5 speed. We are always towing, always in tow haul mode, our tranny usually runs around 170º-180º or so range and our engine coolant runs around 202º-207º. When climbing steep grades they both will go up a bit but come down again fairly quickly when we're not climbing anymore. BTW...last year I replaced our OEM thermostat when I did a coolant change. OEM thermostat was rated to open at 214º. The new one I put in opens at 209º so now I see 202º-207º regularly. When the 214º thermostat was installed previously, I'd see coolant temps in the 212º-217º range and sometime higher when climbing.

If you want to cool down the tranny quickly—like pulling into a rest stop—put it in Park while sitting there for a few minutes before turning off engine. I always practice this anyways as SOP. I give the engine and tranny a 2-3 minutes cool down period before I shut off the engine.

TeJay · 12-09-2020, 09:35 AM

Our RV is on a 2013 chassis and we experience about what you're seeing after you changed your stat to 209 #. Your temps at 212 to 221 seem high to me but then again the industry does change things for one reason or another. Some of it is mileage and some is related to emissions and some is related to who knows what????

We've driven through the NH mountains twice to get into ME and only one time has the clutch fan ever kicked on and that was the first trip through those NH steep hills. Is has never kicked on any other driving time going to FL, MI etc. I've driven school buses all over the place and those fans kick on all the time even going up small rises over a river or train tracks. I understand they are controlled by a thermostat but it's just seemed strange.

mr.tommy · 12-09-2020, 09:22 PM

Quote:

Originally Posted by TeJay

Our RV is on a 2013 chassis and we experience about what you're seeing after you changed your stat to 209 #. Your temps at 212 to 221 seem high to me but then again the industry does change things for one reason or another. Some of it is mileage and some is related to emissions and some is related to who knows what????

We've driven through the NH mountains twice to get into ME and only one time has the clutch fan ever kicked on and that was the first trip through those NH steep hills. Is has never kicked on any other driving time going to FL, MI etc. I've driven school buses all over the place and those fans kick on all the time even going up small rises over a river or train tracks. I understand they are controlled by a thermostat but it's just seemed strange.

Ya well what used to be is over now. I'm loving running at 202º-207º now and my coach loves me for helping her keep a cool head. She's a very dependable rig but I baby her all the time. I find taking care of our coach a labor of luv. Kinda like I did when I got my first car. A yellow 1957 Chevy Bel Air, 283, 3 speed on the column. She never had a scratch on her. I was always working on her and I loved cruising the strip in her on Friday nights. Those were some good days. Now I cruise the CG's in my 2012 35' MH. But now, nobody cares except me.

NXR · 12-10-2020, 09:44 AM

I do not believe there is a direct way to measure transmission temp on the 6-speed, which a 2018 model year has.

I had read that the engine coolant temp is very close to the transmission temp for a reason that escapes me now. My 2019 F53 chassis runs about 204 F for the engine coolant.

For people that are giving a trans temp number, how are you seeing that?

Ray