Thread: Transmission Cooler

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C9, Thank you very much! I am leaving now to pick up some 1.9" OD Al pipe with 0.1" wall and I will play around with an Al cooler and maybe add some fins to it for added surface and looks. Al will anodize black and I am sure there are places in the area that do anodizing. That looks like the ticket for me although there is a pan of some sort acting as a scoop for radiator air in the 'glass body (Bebops). If I keep that scoop/tray and add a front bumper I think I can still mount a spreader bar with trailing edge fins in there, although that puts hot air right into the radiator. It will take a while but I am going to try it. As far as the black surface goes for FMX that comes out of thermodynamics in which a dull black surface can absorb or radiate all wavelengths most rapidly to establish an equilibrium so since a lot of the radiation goes through the metal as infrared radiation and becase heat tends to travel from hotter to cooler, the black surface makes the transfer more rapid to the outside. Yes black aids in absorbing heat also but since the inside is hotter the heat will flow to the outside, the black surface just makes it easire to pass through the surface and eventually the air flow has to carry away the heat. Now all I have to do is some careful fabrication on what should be a relatively simple device. Thanks C9!

Don Shillady
Retired Scientist/teen rodder

I think summit sells a trans cooler with a built in fan for mounting under the vehicle. This might be another idea for you. I think it has a thermostat built in for controlling the fan. The primary market of it is for auxilary cooling for towing, but for a hot rod I think it would be more than enough by itself. Just wanted to throw another idea out for you.

That is the B&M one with the fan. I think he is saying that he doesn't have enough room though. I hear that the ones that go straight under there are not as good though plus I dont trust a nice B&M one with that fan under there in case a rock or something hit's it.

Don, take a look at these coolers.
http://www.alumrad.com/coolers.htm
I bought a 3 ft section of their external finned extrusion and made a under body cooler that ran parallel to the frame (so the air flowed down the fins). We welded bungs on each end.....seems to help. Also had a Derale cooler with an attached fan mounted under the car and horizontal to the ground.....didnt work for flip.

mike in tucson

Far as painting the engine goes, gloss black ought to work fine.
Since it's water cooled the block color and gloss/flat shouldn't make too much difference.

I wouldn't go to the expense to powder coat the block.
There'll be a heck of a lot of prep work to get all the residual oil out.

For painting, a good - multiple - washdown with lacquer thinner or acetone ought to do it for the block if it's clean to start with.

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Don, one thing I forgot about as far as powder coating goes, you can powder coat the bare tube and epoxy in the end caps later.

This pic of my 32's powder coated 'gasser' style rear bumper shows what I did.

The 2 5/8" x .120 wall tube bumper was finished except for the aluminum end caps.

After I got the bumper back from the powder coater I mounted it on the car and then epoxied in the end caps.

Epoxy was applied only to the inside of the bumper and down a little ways so it didn't squeeze out.
The aluminum end caps were cut to fit so they were snug.
Once the aluminum end caps were in the epoxy smeared tubing interior they did not require clamping.

Note that on a smaller tube air pressure could drive them back out a ways so leave a threaded bung open while epoxying.


If you build a mild steel trans cooler/spreader you could do the same.
In fact, you could do it with aluminum if you wished.

JB Weld is good stuff.
I've made some non-critical aircraft parts and JB'd them together with no problems.

The pic shows the basic construction of the 32's rear bumper.
Added for a bit of tap-in-the-rear safety as well as to add a horizontal style line.
with the top up the 32 looks tall and narrow from the back.

Conversely, from the front the top makes it look low and sneaky.

While it is true that black bodies offer improved radiation boundaries for heat transfer it takes relatively extreme thermal gradients to take advantage of this. And of course on a sunny day we always notice black surfaces to be a bit hotter than lighter ones.

That front spreader trans cooler is a super idea. But the primary mechanism for its operation is that oil heat is convected into the tube walls. This heat is then conducted to the surface and convected away from the outside of the tube by the air flowing around it. It may also conduct heat into the chassis out the ends which is also covected away by the air.

In order to maximize its performance (if needed) one would desire to maximize the thermal conductivity of the powder coat/paint on the spreader as well. The paint raises the tube surface temperature as it represents a thermal resistance. As far as heat transfer goes one could also weld circular fins down the length of the bar to increase the conduction/convection area.

Best Regards, Kitz

Eastwood offers two products specifically for painting radiators: 10040Z radiator black ( gloss ) and 10340Z radiator black ( satin ) $10.99 ea

1-800-345-1178

Originally posted by kitz
While it is true that black bodies offer improved radiation boundaries for heat transfer it takes relatively extreme thermal gradients to take advantage of this. And of course on a sunny day we always notice black surfaces to be a bit hotter than lighter ones.

That front spreader trans cooler is a super idea. But the primary mechanism for its operation is that oil heat is convected into the tube walls. This heat is then conducted to the surface and convected away from the outside of the tube by the air flowing around it. It may also conduct heat into the chassis out the ends which is also covected away by the air.

In order to maximize its performance (if needed) one would desire to maximize the thermal conductivity of the powder coat/paint on the spreader as well. The paint raises the tube surface temperature as it represents a thermal resistance. As far as heat transfer goes one could also weld circular fins down the length of the bar to increase the conduction/convection area.

Best Regards, Kitz

Well written and quite true.
But . . . if the cooler/spreader is coated/painted/whatever and cools the trans to a sufficient degree then it's a somewhat moot point.
90% efficient can be ok in some cases.

In this particular case, I didn't want the cooler/spreader to look too far different from a stock spreader.
I like subtle things....


Fwiw - the tube coolers correct name is, "Skin Effect Radiator."

Some WW2 British fighter planes used this skin effect radiation to cool engine oil in oil tanks that conformed to and were a part of the wings leading edge.
They could overheat if too much dinking around on the ground - taxiing, holding, etc. was done, but once in the air they cooled just fine.

Well there going to be a lot of compromises on the road to my car's horizon. I went to a metal company and ended up with some 1 1/2" x 2 1/2" rectangular tubing but the wall thickness is 0.120", prettty thick. I note that with my Bebobs 'glass body there is a built in apron over the frame horns so I can slip in the rectangular tubing under the apron without it being seen at all and then add a row of fins along the bottom edge. This has the advantage of being mostly hidden although it may look like "teeth" or a cow catcher rake along the bottom edge and with that thick wall it should not be bothered by flying gravel and still be above the dropped axle. I also picked iron tubing for easier welding and maybe the main effect is for the increased volume of fluid in the circulating system. By the time you add the volume of the cooler container and the longer hoses to the front site the added volume is of the order of an additional quart so that also helps cooling. With the Brookville frame it also looks like I could route the hoses through the frame rail rectangular tubing if I cut/drill two holes in the frame near the outlets on the transmission. Such holes would have to be about 3/4" diameter and maybe would weaken the frame (?), probably not worth worrying about and the holes would probably have to be elongated to an oval shape to not cut into the right angle bend of the hoses. Anyway I am still listening to other suggestions you have made but I am thinking I may go for a heavy duty finned iron chamber under the front apron. Maybe it will be necessary to use a hole saw for a row of holes in the apron above the cooler; anyway the ideas from C9 are excellent and also indicate that for a light car the cooling can be handled by just surface cooling. Thanks to all for a lot of good ideas. If/when I get a cooler installed I will post a picture.

In edit mode I note that the apron drops down below the top of the frame horns so the cooler would have to be ABOVE the apron. The problem occurs because I don't have the body mounted yet and I have to look at the frame inside the garage and then go outside to the body on the pallet and look/measure there. This also means that the cooler has to be cleaner in appearance since it will be in plane view. Now to study C9's spreader bar some more!

Don Shillady
Retired Scientist/teen rodder

If you can't get round tubing in the wall thickness you want, get a piece of straight exhaust tubing from the muffler shop.
Once it's finished - powder, paint etc. - it'll look just fine.

Like Kitz said, takes a while for the heat to travel.
.120 wall strikes me as too thick.

Far as adding trans oil capacity, the deeper Derale trans pan with air cooling tubes or a B&M stamped pan that's 1" deeper will add about a quart.
(The cast aluminum pans are pretty, but I'd rather have a pan that dented instead of broke.)

Copper pipe with U-connector or a couple of 90's could make you an underframe trans cooler that could be quite long and radiate heat quite well.

Here's another way to add some trans fluid capacity as well as a touch of additional cooling.

The white filter is a common (Fram #) PH8a filter on a single remote adapter and filters trans fluid.
The orange filters are engine oil filters.

Thanks C9, you are too good for me! I went out to the garage to scope out the situation again this morning and you are right, that rectangular ($7) tubing has a wall that is too thick, but then you are not aware of the apron scoop on my all-fenders-and-floorpan glass body from Bebops. In the meantime I found a cooler that had been sent to me by Henry Rifle (nearby, I hope to visit him sometime) and I think that is the easy way out for me with this apron between the frame horns. The cooler is shiny and meant to be a trans cooler and will be in a place which is similar to the bottom of a radiator with a built-in trans cooler. I have learned from several of you that the cooler works better in front of the car and this type cooler is less fragile than a finned in-line cooler as well as being protected from rocks by the apron. Of course the '29 radiator is not very tall (I already bought the radiator) and if I mount my license plate (Va requires a front plate) on top of the cooler it might look a little better but block off air from the bottom of the radiator. On the other hand I will be using an electric radiator fan high up on the inside and if I mount the trans cooler toward the front of the apron about where C9's spreader bar is there will be a gap for air behind the cooler for air flow. I have also learned from several of you including C9 that it is a good idea to put a temperature gauge on the trans fluid. C9 thanks for your excellent ideas, I wish I could run a fenderless roadster, but my compromise with my wife is that the car has to look like a Model-A (with a shiny trans cooler in front!) so I have to deal with this apron-scoop at the bottom of the radiator surround. Please excuse my extra wordiness (verbosity) but I am learning a lot from the chatter. The picture below shows a mockup of the cooler in place.

Don Shillady
Retired Scientist/teen rodder

DennyW, good to hear from you. Under my radiator is really tight with the buggy spring and the cross-steer drag link so I guess I will go with the setup in the picture. Maybe with a natural place for a license plate the cooler will not be as noticeable and maybe even the license plate (aluminum) will give a little more cooling if I bolt it on tight!

Don Shillady
Retired Scientist/teen rodder

That thing with the oil filter idea is awsome! How's that work out? Can you do BOTH with the intil cooler AND that? Denny, I think my inline cooler is like yours there. Also I see your front grill there with the point.... looks awsome heh, I love those grilles.

Don, that cooler looks very nice.

I'm thinking if you go ahead and mount your front license plate - as you can tell Sunny California requires a front plate as well - on the spreader and get it up a little way so oncoming air can bleed under the license plate, that along with the normally turbulent air around the front end should carry heat away very well.

I'm sure you've seen the connecting rod looking spreader bar license plate mounts and that should get you up high enough for air to pass under the plate and directly onto the cooler.
The Deuce Factory is one place that carries them.
They're classy looking and worth the money imho.
(No welding/drilling the spreader bar either.)

Arizona doesn't require a front plate so I run a souvenir plate from last springs Route 66 Fun Run.
I like the looks of the car with a plate on than without.

Not really legal Don, but on a '34 I built a number of years back, I mounted the front license plate on a piano hinge arrangement with a light spiral spring in it. At highway speeds the front plate would simply hinge back and allow full airflow to the radiator and cooler!!!! I'm not sure it helped the cooling all that much, but it certainly made a great conversation piece!!! Another option, if you have the room, is to mount the license plate very low and angled back to act like a wing directing airflow to the radiator.