i run a high output 454 (500hp & 550lb/ft) , TH-400 , NP-205.
the radiator is a two row aluminum taken out of a 6.5 DIESEL Chevy van-dura with two electric fans, cooling
the engine AND the tranny.
do'nt have heating problems - the temps are about 170, and when the engine works hard, it gets to max 200.
i don't have a tranny oil temp gauge so i do'nt know how hot
it gets there.

people keep telling me i need a separate cooler for the
tranny, because it works very hard and the temps here in the summer get up to 105. i used to think that such a radiator from a DIESEL vehicle(compression high as 13-14:1) should be fine also for the tranny, but i'm not sure any more.

would appriciate your input.

i would continue to use the cooler in the radiator and also a separate cooler. this seems to be the setup for an auto that gets used hard.

For my TH400 , I run a dedicated cooler. It is rated for 30,000 gvw
vehicles. I also run a electric fan on it that pushes 1250 cfm. This
set up has worked great for me over the years.

Is this your tow rig??????

If so, then yes, get another cooler, they are cheap and easy to install. If no, then don't worry about it.

Originally posted by elf_cruiser
Is this your tow rig??????


no. i'm talking about the frog with new injected Chevy 454.

i should point out thogh that it weighs a bit more than 6000 lb.

Your Al radiator is an excellent way to help; since the oil cooler coils are also Al it'll transfer heat to the coolant much better. Easy enough to put on a gauge and see how warm the transmission really does get, then make a decision based on a measurement instead of an opinion. However, I second the motion to keep the cooler in the radiator and add another big one downstream (ie. ATF through the radiator first, then the aux. cooler). This is how my 727 is cooled. The stacked-plate variety is very good, B&M sells them, and GM uses them stock on newer rigs; you can probably pick one up in a junkyard for a lot less than having a new one shipped. I also agree with the suggestion to run a separate electric fan just for that trans. cooler, and mount it somewhere other than in front of the radiator - these two things I've not done yet, and need to fix. When I work mine hard, it's clear that the extra heat from the AT cooler does push the engine temperature up. Given a "normal" AT operating temperature of 200-250F, life expectancy is inversely porportional to temperature (above this point). Running them too cold doesn't do 'em any good either.

Originally posted by Lloyd
mount it somewhere other than in front of the radiator- my radiator is back mounted. i forgot to mention that before. because of the extra pipe length i have apprx. 7.5 gallons(!!) of coolant in the system. maybe this is an important factor as well. does such an amount of coolant add to the
cooling capacity:question: :question:

Running them too cold doesn't do 'em any good either. - that's what i was thinking. putting another cooler + electric fan might cause overcooling, especially in "normal" wheeling, something i would'nt want to happen.

i think your idea of putting a temp meter before deciding what to do is a smart one. thanks

Originally posted by Lloyd
Your Al radiator is an excellent way to help; since the oil cooler coils are also Al it'll transfer heat to the coolant much better. Easy enough to put on a gauge and see how warm the transmission really does get, then make a decision based on a measurement instead of an opinion. However, I second the motion to keep the cooler in the radiator and add another big one downstream (ie. ATF through the radiator first, then the aux. cooler). This is how my 727 is cooled. The stacked-plate variety is very good, B&M sells them, and GM uses them stock on newer rigs; you can probably pick one up in a junkyard for a lot less than having a new one shipped. I also agree with the suggestion to run a separate electric fan just for that trans. cooler, and mount it somewhere other than in front of the radiator - these two things I've not done yet, and need to fix. When I work mine hard, it's clear that the extra heat from the AT cooler does push the engine temperature up. Given a "normal" AT operating temperature of 200-250F, life expectancy is inversely porportional to temperature (above this point). Running them too cold doesn't do 'em any good either.

With my aux. trans cooler (30k GVWR) and temp gauge I rarely see temps OVER 170...And that's in a hot canyon...The sending unit is in the front of the pan right at the return line...So I guess my question is what's the problem with running a trans at 100 deg F? Tranny fluid is sooooo viscous I would think that as long as it's not frozen, and running like 30w, it should be fine.

I've heard running a trans too cold is bad...But nobody can tell me why...All I ever get when I ask this question is: "Well, if the auto engineers wanted it that way they would have..." Anyone?

--D

forgot to mention - the radiator is mounted behind the seats. the extra pipe length gives a toal of 7.5(!!) gallons of coolant. do you think this amount of coolant add to the cooling capacity:question::question:


Originally posted by Lloyd
. Easy enough to put on a gauge and see how warm the transmission really does get, then make a decision based on a measurement instead of an opinion. - that's really
a good idea, thanks.

Running them too cold doesn't do 'em any good either. - that's what i was thinking, especially with the electric fan:confused:

sorry for the mess. my p/c has it's own will - it posts what it likes whenever it likes.....:emb2: :emb2: :emb2:

Originally posted by RockRover
With my aux. trans cooler (30k GVWR) and temp gauge I rarely see temps OVER 170...And that's in a hot canyon...The sending unit is in the front of the pan right at the return line...So I guess my question is what's the problem with running a trans at 100 deg F? Tranny fluid is sooooo viscous I would think that as long as it's not frozen, and running like 30w, it should be fine.

I've heard running a trans too cold is bad...But nobody can tell me why...All I ever get when I ask this question is: "Well, if the auto engineers wanted it that way they would have..." Anyone?

--D

With the sending unit in front of the pan at the return line that's a reasonable temp to expect - here you're measuring the temperature of the COOLED fluid. IMHO it's better to measure what's coming out of the transmission; this gives you a better idea of what the transmission temperature is, while your system tells you how well the cooler(s) are working. Largely a matter of personal preference.

100F is too cold to drive out the water vapor; ATF is mildly hygroscopic - it absorbs water out of the atmosphere and then corrodes all the internals. Since you've got an assortment of dissimilar metals in an AT (Al, Fe, and brass, at least) the presence of a conductive fluid in contact with all of these metals creates a battery, and the electrochemical reactions just eat it up.

Originally posted by the frog
forgot to mention - the radiator is mounted behind the seats. the extra pipe length gives a toal of 7.5(!!) gallons of coolant. do you think this amount of coolant add to the cooling capacity:question::question:


All that extra coolant will add to the heat capacity of the cooling system - ie. it will take much more energy to change the temperature of the system; longer to heat up, longer to cool down. Suppose you're climbing a steep loose hill for 1/2 mile; your temperature rise at the end of that climb will be considerably less than the same rig with a normal quantity of coolant in the system. You've also got to consider the heat capacity of the block and heads, etc; probably 700 lbs of iron in your case. For reference, at 30 C the heat capacity of iron is 452 J/(kg deg. K) and for water it's 4178 J/(kg deg. K)

Originally posted by Lloyd


probably 700 lbs of iron in your case

aluminum heads and intake manifold. dont think it weighs more than a 350 with iron heads. the heat dissipation of the aluminum parts is probably much higher.

thanks for the explanation & example of what happens with more coolant - it was new to me, and very interesting.:beer: :beer:

Originally posted by high5
i would continue to use the cooler in the radiator and also a separate cooler. this seems to be the setup for an auto that gets used hard.
Same setup I use, and its worked GREAT for my auto tranny.
Scott

For aluminum the heat capacity is 900 J/(kg deg. K). Thermal conductivities are 2370 W/(m deg. K) for aluminum and 803 for iron. So aluminum has twice the heat capacity and three times the thermal conductivity of iron - yes, it'll cool better. While we're at it, the heat capacity for copper is 383 and its thermal conductivity is 3980 - same units. So, a given amount of heat will raise the temperature of some mass of copper more than the same mass of aluminum, but the copper will conduct the heat better. In all of this, the real gotcha is that the same parts made out of different metals NEVER weigh the same, so if you're going to try to do something with all this you need the all the masses of the different parts too.

My personnal opinion is that you would want to run an extra cooler but it should actually run through the radiator cooler after.This allows quicker warmup for the tranny and will keep it within normal operating perameters.This method is also less taxing on the radiator cooler so even normal running temps are the norm even when working it hard.