Tranny Temps
#31
07-12-2011 | 11:33 PM
Captain
Joined: Sep 2008
Posts: 626
Likes: 1
From: Colorado Springs
"No"...to clarify, aluminum is capable of absorbing and dissipating heat "much" faster than steel..."thats my point".That's why we use aluminum frying pans...they cook faster, distribute heat faster, and cool off faster than steel pans do. And that's why it's best to use an aluminum tranny pan, to absorb the heat get it away as fast as possible. Everyone knows that steel is capable of absorbing more heat than aluminum, but that has nothing to do with this. And the fins are there to help distribute the "ambient" (meaning controlled temperature) air across the pan cooling the fins which cool the pan which cools the fluid. Don't try and clean up your "truth be told, ambient temperature has little affect on this stuff" Everything about the temperature is ambient contolled by liquid, radiators, fins, fans and thermostats from under the hood to under the car. But you're right about one thing, and that's what I've been saying all along...aluminum (tranny housing) conducts heat from the source...the engine, lol! 
#32
07-12-2011 | 11:55 PM
Captain
Joined: May 2009
Posts: 731
Likes: 1
From: Louisiana
Part of the problem is that he doesn't seem to understand "absorbing" vs. "conducting"...
Steel will absorb more because it has higher melt temps - but it's not as good a conductor.
If you can't give good basic information, don't polute the pool.. You have to understand the basics, first. Don't explain thermodynamics, unless you understand it.
Read, and research, and understand are key to good explanations.
Steel will absorb more because it has higher melt temps - but it's not as good a conductor.
If you can't give good basic information, don't polute the pool.. You have to understand the basics, first. Don't explain thermodynamics, unless you understand it.
Read, and research, and understand are key to good explanations.
#33
07-13-2011 | 12:53 AM
Captain
Joined: May 2009
Posts: 731
Likes: 1
From: Louisiana
I know from my heat sink design and experience in electronics that you are correct about steel versus aluminum with respect to thermal conductivity. If I may, I would like to add to your explanation about the role of heat sink fins. Their role is twofold actually, they allow for the channeling of air across the heat sink (Transmission pan) in an efficient manor and they effectively increase the surface area of the heat sink. Thick aluminum (as much mass as possible) with the most possible surface area possible (fins) is an ideal scenario in heat sink design. Ambient temperature has *everything* to do with how well a heat sink can conduct heat away from a load - you are absolutely correct in this regard as well. There is plenty of math to fully support these conclusions if one is interested.
#34
07-13-2011 | 11:17 AM
Record Breaker
Joined: Jan 2010
Posts: 1,400
Likes: 5
From: San Pedro, California
Part of the problem is that he doesn't seem to understand "absorbing" vs. "conducting"...
Steel will absorb more because it has higher melt temps - but it's not as good a conductor.
If you can't give good basic information, don't polute the pool.. You have to understand the basics, first. Don't explain thermodynamics, unless you understand it.
Read, and research, and understand are key to good explanations.
Steel will absorb more because it has higher melt temps - but it's not as good a conductor.
If you can't give good basic information, don't polute the pool.. You have to understand the basics, first. Don't explain thermodynamics, unless you understand it.
Read, and research, and understand are key to good explanations.
Thermal energy can be stored in a material as sensible heat by raising its temperature. The heat storage can be calculated as
q = V ρ cp dt
= m cp dt (1)
where
q = sensible heat stored in the material (J, Btu)
V = volume of substance (m3, ft3)
ρ = density of substance (kg/m3, lb/ft3)
m = mass of substance (kg, lb)
cp = specific heat capacity of the substance (J/kgoC, Btu/lboF)
dt = temperature change (oC, oF)
= m cp dt (1)
where
q = sensible heat stored in the material (J, Btu)
V = volume of substance (m3, ft3)
ρ = density of substance (kg/m3, lb/ft3)
m = mass of substance (kg, lb)
cp = specific heat capacity of the substance (J/kgoC, Btu/lboF)
dt = temperature change (oC, oF)
#35
07-13-2011 | 12:26 PM
Captain
Joined: Sep 2008
Posts: 626
Likes: 1
From: Colorado Springs
First of all, if you are going to declare yourself an expert on this subject, then I recommend you follow your own advice and research the subject. The correct term for heat retention in materials is "Heat Capacity" not "absorbing".
Thermal energy can be stored in a material as sensible heat by raising its temperature. The heat storage can be calculated as
Thermal energy can be stored in a material as sensible heat by raising its temperature. The heat storage can be calculated as
q = V ρ cp dt
= m cp dt (1)
where
q = sensible heat stored in the material (J, Btu)
V = volume of substance (m3, ft3)
ρ = density of substance (kg/m3, lb/ft3)
m = mass of substance (kg, lb)
cp = specific heat capacity of the substance (J/kgoC, Btu/lboF)
dt = temperature change (oC, oF)
= m cp dt (1)
where
q = sensible heat stored in the material (J, Btu)
V = volume of substance (m3, ft3)
ρ = density of substance (kg/m3, lb/ft3)
m = mass of substance (kg, lb)
cp = specific heat capacity of the substance (J/kgoC, Btu/lboF)
dt = temperature change (oC, oF)
Ta (ambient) is also an important factor:
Tr - Temperature rise
Ta - Ambient temperature
Th - Heatsink temperature
Ph - Power applied to heatsink
Rth - Thermal resistance (in °C/W)
Tr = Th - Ta
It is interesting to note the role of surface area. To reduce the heatsink temp by 50% you must quadruple the surface area, that is where finning comes in handy
#36
07-13-2011 | 12:30 PM
Veteran
Joined: Dec 2010
Posts: 422
Likes: 0
From: North Aurora, Il - 40 miles west of Chicago
I'm not trying to post expert credentials - but I do a lot of research before I offer advice, if I don't already know the correct answer - it was a requirement in my job, prior to retirement.
Things like heat always radiates toward cold, conduction of heat away from one thing to another, etc.
I was using "absorbing"(his term, not mine) to differentiate the absorbtion(capacity,) vs, conduction - which is what was trying to be explained. There's a big difference.
I understand that ambient temperatures have bearing, but not at this small of a spread.... 90 degrees, vs 120-130 or so F. These temps are already in the design parameters of the stuff being discussed.
I certainly wasn't differing with you Pedro, just trying to clarify what was being postulated.
I'm just trying to maintain good information going out.
Things like heat always radiates toward cold, conduction of heat away from one thing to another, etc.
I was using "absorbing"(his term, not mine) to differentiate the absorbtion(capacity,) vs, conduction - which is what was trying to be explained. There's a big difference.
I understand that ambient temperatures have bearing, but not at this small of a spread.... 90 degrees, vs 120-130 or so F. These temps are already in the design parameters of the stuff being discussed.
I certainly wasn't differing with you Pedro, just trying to clarify what was being postulated.
I'm just trying to maintain good information going out.
Last edited by WNDERR; 07-13-2011 at 12:36 PM.
#37
07-13-2011 | 12:42 PM
Record Breaker
Joined: Jan 2010
Posts: 1,400
Likes: 5
From: San Pedro, California
WNDERR, I was a little frustrated with the direction the thread took. Seemed to me it was becoming a pissing contest and very little of value was been added. My background as an engineer with over 30 years in the business got the best of me. All is good, I appreciate all of the inputs. I must admit a lot of this was fun - and free.
#38
07-13-2011 | 01:21 PM
Registered User
Joined: May 2011
Posts: 13
Likes: 0
No pissing contest update here, just a data point.
I took my Ram on its first towing trip over the weekend. 2011 Sport w/Hemi and 3.55 gears, bone stock. My tow load is a small RV, about 3500 lbs loaded. I took a 100 mile "test tow" the weekend before the big trip to put some slow miles on her - I kept it under 50 as the manual stated. As the trip started, I kept it under 50 for another 100 or so miles, which was all flat (I-10/12 across LA - the state, not the city). In tow/haul mode, I was able to roll easily in 5th.
Turning up I-59 in to MS, where the rolling hills begin, I kicked it up towards 55, and had to use 4th (less lugging, better instantaneous fuel consumption). Continuing up to Chattanooga and over into the mountains of WNC I towed as high as 60, but never higher except for short spells when I was in heavy traffic around cities where going slower seemed more hazardous. I continued to use 4th, though I occasionally tried 5th, or even flipping off tow/haul to see if I could benefit from OD on downhills. The answer? No.
The point? The only time I saw temps over 150 were when I tried 5th or no tow/haul - that is, when the tranny was shifting too frequently. My (amateur) understanding is that a transmission's worst enemy is heat, and the major contributor to heat is frequent shifts, as things are cooler when the tranny can enter "lockout". IMHO, tow/haul helps this situation greatly. If you are seeing high temps, I've read that it's essential to shorten the transmission service intervals accordingly. Whether it's fluff by the people that sell transmission fluid or not, I've seen charts that show the decrease in fluid life expectancy for raises in running temp. It may be cheap insurance...
I took my Ram on its first towing trip over the weekend. 2011 Sport w/Hemi and 3.55 gears, bone stock. My tow load is a small RV, about 3500 lbs loaded. I took a 100 mile "test tow" the weekend before the big trip to put some slow miles on her - I kept it under 50 as the manual stated. As the trip started, I kept it under 50 for another 100 or so miles, which was all flat (I-10/12 across LA - the state, not the city). In tow/haul mode, I was able to roll easily in 5th.
Turning up I-59 in to MS, where the rolling hills begin, I kicked it up towards 55, and had to use 4th (less lugging, better instantaneous fuel consumption). Continuing up to Chattanooga and over into the mountains of WNC I towed as high as 60, but never higher except for short spells when I was in heavy traffic around cities where going slower seemed more hazardous. I continued to use 4th, though I occasionally tried 5th, or even flipping off tow/haul to see if I could benefit from OD on downhills. The answer? No.
The point? The only time I saw temps over 150 were when I tried 5th or no tow/haul - that is, when the tranny was shifting too frequently. My (amateur) understanding is that a transmission's worst enemy is heat, and the major contributor to heat is frequent shifts, as things are cooler when the tranny can enter "lockout". IMHO, tow/haul helps this situation greatly. If you are seeing high temps, I've read that it's essential to shorten the transmission service intervals accordingly. Whether it's fluff by the people that sell transmission fluid or not, I've seen charts that show the decrease in fluid life expectancy for raises in running temp. It may be cheap insurance...
#40
07-13-2011 | 04:14 PM
Rookie
Joined: Aug 2010
Posts: 58
Likes: 0
From: Ontario
No pissing contest update here, just a data point.
I took my Ram on its first towing trip over the weekend. 2011 Sport w/Hemi and 3.55 gears, bone stock. My tow load is a small RV, about 3500 lbs loaded. I took a 100 mile "test tow" the weekend before the big trip to put some slow miles on her - I kept it under 50 as the manual stated. As the trip started, I kept it under 50 for another 100 or so miles, which was all flat (I-10/12 across LA - the state, not the city). In tow/haul mode, I was able to roll easily in 5th.
Turning up I-59 in to MS, where the rolling hills begin, I kicked it up towards 55, and had to use 4th (less lugging, better instantaneous fuel consumption). Continuing up to Chattanooga and over into the mountains of WNC I towed as high as 60, but never higher except for short spells when I was in heavy traffic around cities where going slower seemed more hazardous. I continued to use 4th, though I occasionally tried 5th, or even flipping off tow/haul to see if I could benefit from OD on downhills. The answer? No.
The point? The only time I saw temps over 150 were when I tried 5th or no tow/haul - that is, when the tranny was shifting too frequently. My (amateur) understanding is that a transmission's worst enemy is heat, and the major contributor to heat is frequent shifts, as things are cooler when the tranny can enter "lockout". IMHO, tow/haul helps this situation greatly. If you are seeing high temps, I've read that it's essential to shorten the transmission service intervals accordingly. Whether it's fluff by the people that sell transmission fluid or not, I've seen charts that show the decrease in fluid life expectancy for raises in running temp. It may be cheap insurance...
I took my Ram on its first towing trip over the weekend. 2011 Sport w/Hemi and 3.55 gears, bone stock. My tow load is a small RV, about 3500 lbs loaded. I took a 100 mile "test tow" the weekend before the big trip to put some slow miles on her - I kept it under 50 as the manual stated. As the trip started, I kept it under 50 for another 100 or so miles, which was all flat (I-10/12 across LA - the state, not the city). In tow/haul mode, I was able to roll easily in 5th.
Turning up I-59 in to MS, where the rolling hills begin, I kicked it up towards 55, and had to use 4th (less lugging, better instantaneous fuel consumption). Continuing up to Chattanooga and over into the mountains of WNC I towed as high as 60, but never higher except for short spells when I was in heavy traffic around cities where going slower seemed more hazardous. I continued to use 4th, though I occasionally tried 5th, or even flipping off tow/haul to see if I could benefit from OD on downhills. The answer? No.
The point? The only time I saw temps over 150 were when I tried 5th or no tow/haul - that is, when the tranny was shifting too frequently. My (amateur) understanding is that a transmission's worst enemy is heat, and the major contributor to heat is frequent shifts, as things are cooler when the tranny can enter "lockout". IMHO, tow/haul helps this situation greatly. If you are seeing high temps, I've read that it's essential to shorten the transmission service intervals accordingly. Whether it's fluff by the people that sell transmission fluid or not, I've seen charts that show the decrease in fluid life expectancy for raises in running temp. It may be cheap insurance...