DT RAM 1500 5.7L towing oil temps

OVERKILL

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Had my dad snap this shot of the cluster while I was towing the boat up to the cottage. Most of the trip was spent in 7th (tow/haul limits 8th to above 100Km/h) with it being in 8th once we got onto highway 11.

This is not a super heavy load, probably around 4,500lbs combined? A fair bit lighter than our Four Winns, which isn't quite ready to go up to the lake yet.

This truck has the 3.92 rear axle ratio with tow package (trailer brake controller...etc) and oil cooler.

I also had him snap a pic of oil pressure. This is M1 EP 0w-20. Relief pressure on the pump is 75psi, a downshift to 6th to accelerate put it up around 3K and 55psi.

For those not using metric, 108C is 226F, which is quite reasonable. As you can see, ambient temp is quite warm (33C/91.5F) which likely explains the higher observed temp than I saw in the fall when it was much cooler. OE thermostat opening temp is 195F IIRC.

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OVERKILL

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That seems a bit high to me. My 07 Silverado doesn't get over 185F when towing, but I assume it has a big aux cooler.
Coolant/trans fluid heat exchanger, so trans temp stays very close to coolant temp, just like oil temp. Yours sounds like it just has an aux cooler unless you are running a cooler than stock thermostat?
 

OVERKILL

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Stock thermostat far as I know. I remember reading somewhere that for every 10 degrees over 170F transmission temperature, transmission life drops 10%.

Then you likely don't have a coolant/trans fluid heat exchanger. These are becoming more and more common as they heat up the trans fluid as the coolant heats and then holds it around coolant temp, which is supposed to be "optimal". This is why we have coolant/oil heat exchangers as well.

That might have been a rule of thumb for a TH350 or something back in the days of Dex III, but modern ATF's are designed around their intended operating temp, so I would assume that with the ZF unit designed to be run at the temps it sees, that the ZF lifeguard fluid is more than capable of standing up for the long haul at those temps.
 
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Stock thermostat far as I know. I remember reading somewhere that for every 10 degrees over 170F transmission temperature, transmission life drops 10%.
The 70s called and want their information back. Modern transmissions, and ATF, run at much higher temperatures. 2019 tundras even had their coolers removed and Toyota considers up to 270f “normal”, when towing.
 
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Stock thermostat far as I know. I remember reading somewhere that for every 10 degrees over 170F transmission temperature, transmission life drops 10%.

Don't look now but most modern transmissions run much hotter than that... The 6r80 in my F150 (and my old V8 Explorer) normal temp was 200-210F. It has a 190 Degree thermostat to send fluid to the cooler...

I would have agreed with you on an old school 4 speed, but we aren't there anymore...
 
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I would have agreed with you on an old school 4 speed, but we aren't there anymore...
My 07 isn't exactly old school, 6 speed Hydramatic, and over 210,000 miles on the original (far as I know) transmission and used as tow vehicle. Suspect cool transmission fluid usually under 170 and rarely over 180, might have something to do with it.
 
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And I got the same service out of 6R80's running temps 200-210, and hotter while towing with miles over 200k too...

Point being the old advice of a blanket temp going across all makes and models means nothing...
 

ls1mike

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I would say based off your ambient air temp you are fine. I know my gas 3500HD the transmission does not see over 175 even in temps over 100 degree temps, but the HD truck has no thermostat for the transmission. Heat kills transmission. I would get worried if you were seeing 220 or over regularly.
HD trucks do not run that hot all. Normally I see 135. Towing without long hills or heat maybe 150ish. The temp has more to do with fluid then the components, but hot/burnt fluid over 230 for periods will kill a transmission. DEX VI good but it will start to break down over 230 at longer periods.
Here is what GM says.
OIL TEMPERATURE MEASURED AT CONVERTER OUTLET TO COOLER.

300F is the maximum temperature. (Workhorse says 350F). This is the normal place to install a temperature gauge or signal. The temperature in this location will vary significantly with each vehicle start-up or hill. If the temperature reaches 300F (350F), reduce throttle. To lower the transmission temperature with the transmission in NEUTRAL, run the engine at 1,200 RPM for 2-3 minutes to cool the oil. Do not allow the converter outlet temperature to exceed 300F (350F).
Keep a close check to prevent the engine cooling system from overheating.

300F would be typical of rocking the vehicle in mud, snow, or sand, or a transmission in stall (full throttle, no vehicle movement). When the transmission is in stall, the transmission will develop heat at a rate of one degree per second of stall.

OIL TEMPERATURES MEASURED IN THE SUMP

150F -- Minimum operating temperature for continuous operation. It is possible in low ambient temperature to overcool the transmission with oil to air-type coolers; it is hard to overcool if used in conjunction with oil to water coolers installed in most standard automotive radiators.

190F-200F -- Maximum oil level checking temperature. Beyond this, readings are not reliable because of expansion.

285F -- Maximum sump/oil pan temperatures for short duration such as a long hill climb.

300F -- Metal parts inside the transmission begin to warp and distort in varying degrees, seals melt rapidly, and transmission fluid life is extremely short due to oxidation and distress.

AUTOMATIC TRANSMISSION FLUID OXIDATION Automatic transmission fluid
can provide up to 100,000 miles of service before oxidation occurs under normal operating temperatures of about 170F. Above normal operating temperatures, the oxidation rate doubles (useful life of the fluid is cut in half) with each 20 degree increase in temperature. The approximate life expectancy at various temperatures is a follows:
Degrees F Miles
175 100,000
195 50,000
212 25,000
235 12,000
255 6,000
275 3,000
295 1,500
315 750
335 325
375 80
390 40
415 Less than 30 minutes

After-market temp gauge should be installed in the lower (hot) line entering the lower fitting of the radiator.

After-market external oil to air cooler should be installed in series. The hot oil line should go first through the aftermarket cooler then into the radiator to maintain proper minimum temp of the trans in low ambient temps.”
 
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The F150 with a 10r80 and a C1500 with the 6l90 both ran around 215 towing. Even running the living daylights out of them on >12% grade hills, I never saw more than 220 on the trans temp. Newer transmissions like to be warm.
 

ls1mike

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The F150 with a 10r80 and a C1500 with the 6l90 both ran around 215 towing. Even running the living daylights out of them on >12% grade hills, I never saw more than 220 on the trans temp. Newer transmissions like to be warm.
Your 1500 had/has a 6L80E, 90E is used in 3/4 ton and up trucks and vans, CTSV-V and Camaro ZL1, none of them to my knowledge use a thermostat.
The 6L80E in you 1500 has smaller cooler and thermostat. The 6L80E is in half tons, Corvettes, Camaro, G8, Caprices.
 

OVERKILL

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Just another ZF 8HP reference, this was my SRT driving home from work today:
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That's like 15 minutes of driving, 180F.
 
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I actually looked at my oil/trans temps towing my jon boat today and the oil was 212f and the trans was 195f. Those are just normal temps It wasnt hot outside and my boat barely counts as a load.
 
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Your 1500 had/has a 6L80E, 90E is used in 3/4 ton and up trucks and vans, CTSV-V and Camaro ZL1, none of them to my knowledge use a thermostat.
The 6L80E in you 1500 has smaller cooler and thermostat. The 6L80E is in half tons, Corvettes, Camaro, G8, Caprices.
Ah, got it Not a GM guy.

The 1500s definitely have thermostats. I was so impressed with the truck I started looking at them. Was really surprised when I saw they had a thermostat. A lot of people seem to remove them.
 
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