We just came back from a week of camping, driving from Colorado Springs to Ridgway State Park near Ouray and back. We drove Hwy 50 over Monarch Pass. This was our first time going over a truly high mountain pass. In the past we have gone over Le Veda and Wilkerson Pass and I never saw transmission temperature over 205. This trip, going west bound in 2nd gear at 40 to 45 MPH, the transmission temperature got to 232 at top of the Monarch Pass. We then stopped to ride the cable car up to the pass summit to see the view and also let the tranny cool down since I don't know if that's too hot or not. Coming back home today east bound on Monarch Pass, I was slower, between 2nd and 1st gear, and the tranny still got to 225 at the summit. I do have an after market tranny cooler installed last year. This is towing pretty close to GCWR of my Suburban. I never saw any warning light. However when I stopped at summit (to ride the cable car), I did smell a bit of burning outside of the Suburban. Usually cruising rolling hills towing the TT, it doesn't get above 190 much. So what's too hot? Is 232 causing damages?

High temp alarm S/B 250*FTranny really have to work hard on those mtn. passes especially when total load is at GCVWRHigh sustained temps never good.

That chart is ancient history !I worked in transmission engineering for one of the Big 3 back in the 80s. Even THEN, sustained temps under 230F were hot, but did not cause fluid or component failure.Today, almost ALL transmission fluid is synthetic or synthetic blend and can comfortably handle 250F. Under 200F is ridiculous because most transmission coolers are inside the radiator and the engine coolant temperature is typically over 200F !Don't get me wrong. Yes, you should check your transmission fluid regularly, more often if you are towing or carrying heavy loads. If it smells burnt or is NOT bright cherry red, it is time for a change. And use the EXACT fluid recommended by the manufacturer, Skip the "boutique" stuff !Sure, keep it cool is the best policy, but lets be realistic !!

theoldwizard1 wrote:That chart is ancient history !I worked in transmission engineering for one of the Big 3 back in the 80s. Even THEN, sustained temps under 230F were hot, but did not cause fluid or component failure.Today, almost ALL transmission fluid is synthetic or synthetic blend and can comfortably handle 250F. Under 200F is ridiculous because most transmission coolers are inside the radiator and the engine coolant temperature is typically over 200F !Don't get me wrong. Yes, you should check your transmission fluid regularly, more often if you are towing or carrying heavy loads. If it smells burnt or is NOT bright cherry red, it is time for a change. And use the EXACT fluid recommended by the manufacturer, Skip the "boutique" stuff !Sure, keep it cool is the best policy, but lets be realistic !!IDK. I added a large trans cooler in series with the stock GM cooler.If I sit and idle with the silveradi the trans temp will match the coolant temp of 190f - 200f.But driving to florida ( was 100 F outside most days) I crused at 160f trans temps and 190- 200f coolant temps.Here is screen shot. This was in GA getting into florida crusing 75 mph at 11500 lbs. Going in the smoky moantains the truck got hotter then the trans did. I think the truck got around 230-240f pulling grade to 5000ft and the trans never went over 190f.Heres a vid pulling mountain grade. 1st gear 3500 RPM 30 MPH.trans 175fCoolant 230fhttps://www.flickr.com/photos/93289479@N04/shares/GvSNN4And trans cooler I moved factory unit down below the bowtie emblemPut the biggest I could fit next to it.Good thing is with A/C on the cooling fans run. I dont think we had the A/C off the whole trip..I belive over 200F for a trans is too hot.

I agree that the chart is certainly outdated, but heat is the enemy. Blanket statements seem to be a thing of the past with full synthetic fluids.Electric cooling fans in my new Ford Powerstroke don't turn on until about 230. Normal operating temps on highway (not towing) are just under 200 for transmission and about the same for engine oil. Normal temps this high are new to me. Reports of 230 going over mountain passes are about average....at least for the Powerstroke. Further, even at those temps, the Ford 6 speed diesel engine transmissions HAVE NO DRAIN AND FILL REQUIREMENT UNTIL 150,000 miles, even under severe duty. Heat seems to be factored in.Having said that, I was always amazed at how cool my 2011 Duramax Allison Transmission ran. Never saw 200 even over high mountain passes. For the op, it is going to depend on the cooling scheme and fluids used by your manufacturer. Lots of different normals out there now.

None of those chart relate to modern ATF and Transmissions. 235...not much worry. None at all if its not a sustained temp. I've had Honda's hit 240 while towing for very brief periods and that's exiting the trans. Which is important to know, because ATF temps are suppose to be measured after the cooler or near the sump. So while some may see a 240 reading, they may not know where that reading is derived from making their concern unwarranted. Also note, Toyota Tundras and Sequoia's have a thermostat that keeps ATF around 200 at all times. Only recently did I find an app that will monitor highs and lows as the add in temp monitor I had in my Honda. And in all the towing I did in recently in day time temps reaching 121, the ATF temp gauge never budged. It appears automotive engineers might know what their doing.

Transmission temperature question | Good Sam Community

EnzoColorado
Explorer II
Jul 28, 2017
Okay so sounds like the temperature I hit should be okay, especially since it was only over 15 minutes or so during the trip. Thanks everyone!
Sandia_Man
Explorer II
Jul 28, 2017
Being that we live and do most of our RVing in the four corner states we have hit those temps as well on occasion. Mentioned it to our mechanic at least a couple of times in the past and he didn't even blink, just said it was typical under extreme duty and synthetic transmission fluid could handle it. As a precaution I have a total tranny fluid flush every 25K miles although the last time we did it our mechanic said our tranny fluid was pink and still had plenty of life.
Dennis12
Explorer
Jul 28, 2017
Pic looks more like one of them air stills than a transmission cooler. Where ya live.
DiskDoctr
Explorer
Jul 28, 2017
Recently it was confirmed by a very reliable source that the Ford 4R100 transmissions used in many of the older SuperDutys were good for 250F for 30 mins.

If hotter, give it a break and let it idle while stopped, preferably fast idle, until it cools down.

With the 6.0 cooler upgrade to my 7.3L Excursion, even when pushing a lot for extended periods, I never saw 200F.

Hope this helps.
TurnThePage
Explorer
Jul 28, 2017
The transmission temp in my last truck regularly climbed to just over 250F during long climbs. I was initially worried but there was never any detectable harm.
DustyR
Explorer
Jul 28, 2017
I was told the transmission temp should be within 100* over the ambient temp. I don't know how reliable that is. IMHO
RinconVTR
Explorer
Jul 28, 2017
None of those chart relate to modern ATF and Transmissions.

235...not much worry. None at all if its not a sustained temp.

I've had Honda's hit 240 while towing for very brief periods and that's exiting the trans. Which is important to know, because ATF temps are suppose to be measured after the cooler or near the sump. So while some may see a 240 reading, they may not know where that reading is derived from making their concern unwarranted.

Also note, Toyota Tundras and Sequoia's have a thermostat that keeps ATF around 200 at all times. Only recently did I find an app that will monitor highs and lows as the add in temp monitor I had in my Honda. And in all the towing I did in recently in day time temps reaching 121, the ATF temp gauge never budged. It appears automotive engineers might know what their doing.
NHIrish
Explorer
Jul 28, 2017
I agree that the chart is certainly outdated, but heat is the enemy. Blanket statements seem to be a thing of the past with full synthetic fluids.

Electric cooling fans in my new Ford Powerstroke don't turn on until about 230. Normal operating temps on highway (not towing) are just under 200 for transmission and about the same for engine oil. Normal temps this high are new to me. Reports of 230 going over mountain passes are about average....at least for the Powerstroke. Further, even at those temps, the Ford 6 speed diesel engine transmissions HAVE NO DRAIN AND FILL REQUIREMENT UNTIL 150,000 miles, even under severe duty. Heat seems to be factored in.

Having said that, I was always amazed at how cool my 2011 Duramax Allison Transmission ran. Never saw 200 even over high mountain passes.

For the op, it is going to depend on the cooling scheme and fluids used by your manufacturer. Lots of different normals out there now.
lawrosa
Explorer
Jul 28, 2017
theoldwizard1 wrote:
That chart is ancient history !

I worked in transmission engineering for one of the Big 3 back in the 80s. Even THEN, sustained temps under 230F were hot, but did not cause fluid or component failure.

Today, almost ALL transmission fluid is synthetic or synthetic blend and can comfortably handle 250F. Under 200F is ridiculous because most transmission coolers are inside the radiator and the engine coolant temperature is typically over 200F !

Don't get me wrong. Yes, you should check your transmission fluid regularly, more often if you are towing or carrying heavy loads. If it smells burnt or is NOT bright cherry red, it is time for a change. And use the EXACT fluid recommended by the manufacturer, Skip the "boutique" stuff !

Sure, keep it cool is the best policy, but lets be realistic !!

IDK. I added a large trans cooler in series with the stock GM cooler.

If I sit and idle with the silveradi the trans temp will match the coolant temp of 190f - 200f.

But driving to florida ( was 100 F outside most days) I crused at 160f trans temps and 190- 200f coolant temps.

Here is screen shot. This was in GA getting into florida crusing 75 mph at 11500 lbs.

Going in the smoky moantains the truck got hotter then the trans did. I think the truck got around 230-240f pulling grade to 5000ft and the trans never went over 190f.

Heres a vid pulling mountain grade. 1st gear 3500 RPM 30 MPH.

trans 175f
Coolant 230f

https://www.flickr.com/photos/93289479@N04/shares/GvSNN4

And trans cooler I moved factory unit down below the bowtie emblem

Put the biggest I could fit next to it.

Good thing is with A/C on the cooling fans run. I dont think we had the A/C off the whole trip..

I belive over 200F for a trans is too hot.
theoldwizard1
Explorer II
Jul 28, 2017
That chart is ancient history !

I worked in transmission engineering for one of the Big 3 back in the 80s. Even THEN, sustained temps under 230F were hot, but did not cause fluid or component failure.

Today, almost ALL transmission fluid is synthetic or synthetic blend and can comfortably handle 250F. Under 200F is ridiculous because most transmission coolers are inside the radiator and the engine coolant temperature is typically over 200F !

Don't get me wrong. Yes, you should check your transmission fluid regularly, more often if you are towing or carrying heavy loads. If it smells burnt or is NOT bright cherry red, it is time for a change. And use the EXACT fluid recommended by the manufacturer, Skip the "boutique" stuff !

Sure, keep it cool is the best policy, but lets be realistic !!