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Here is a question about heat dissipation that has been rattling around in my head for some time.

Is there a benefit to painting the transmission oil pan black, or even the whole transmission, for better heat dissipation? I come to this notion because radiators and oil coolers seem to always be painted black.

Presenting the other side of the question: What about using aluminum or white paint?

Does the paint color make any difference in the heat dissipation of the transmission?

Are the Ultramatics any more sensitive to oil temperature than other automatic transmissions from those days?

Just curious.

A layer of paint contains a polymeric material which, though perhaps modest in performance, is an insulating compound. So just from the standpoint of heat transfer, no paint is the best choice. However, with ordinatry heat-measuring IR guns, I doubt very much you'd be able to see a difference between a modestly thin layer of paint and no paint.

Black will absorb IR radiation and thus become heated, but since the sun don't shine under the car, it's a non-issue. Visa versa for white. Since the metallic flakes (and even metallic pigments) in a paint are insulated by surrounding polymer, I doubt they have much of a chance to enhance heat transfer, if so it's probably so minor it's not measureable except with some more sophisticated instruments than most of us might have.

The standard Ultramatic trans cooler was more than adequate in it's day, even for trailer-towing. I assume it was cooled as well or better than it's contemporaries except for the very first PowerGlides which I believe had no cooler and suffered the consequences. But as time passes, thermal efficiency often deteriorates, so if you have problems which you can attribute to the stock cooler, then either get a new one, service it internally (not fun), or use an aftermarket unit as others have suggested. You could perhaps also adapt an in-radiator-bottom-tank unit from a modern car. From the 3 Ultramatic cars I've owned over the years and driven lots of miles in (certainly more than 100,000), I never had a problem with the cooler.

Really, I hope I'm wrong but I do suspect that the other recent thread about overheated fluid wasn't necessarily due to the cooler, but to broken sprag clutch, or failure of the direct drive clutch to engage so the torque converter, rather than just going along for a free ride, continued to churn, thus creating all the excess heat. At least I think you should check into this possibility.

Throttle pressure linkage set properly? Ultramatics are VERY sensitive to that adjustment.

Not sure color has any advantage other than looks. Radiator paints are usually specially formulated to provide better heat transfer. The one Eastwood sells (at double the cost) is thinner having less pigment to provide less insulation according to the propaganda. Think adequate air flow is more important.

Don't believe Packards were any worse as to making heat but do believe they were a little more critical to thinner fluid because of the bushings. Some of the other transmissions used more tubing and case passages to route the fluid, wheras while Packard did this when possible, due to their design so much depended upon using a rotating hollow or drilled shaft with rings riding in bushings to supply piston pressures.

The oil cooler was standard--maybe not as efficient as some--after all the water was already at a minimum 160 degrees and the exchange area fairly small--but still helpful. Other cars had no coolers--just a finned torque converter to dissipate the heat.

Thanks Owen and HH56. So the fact that radiators are painted black has nothing to do with heat transfer properties. The special thin/low pigment paints are just for appearance sake. I believe the new aluminum core and plastic tank radiators are no longer painted; although, the tanks are black in color. Aluminum transmission cases and cylinder heads are considered more efficient in their ability to transfer heat than their cast iron counterparts. So, it is the material not the finish that determines a component's ability to transfer heat. Enough of this, thanks again.

So, it is the material not the finish that determines a component's ability to transfer heat

Yes, within reason and as long as we ignore differences so small they are insignificant; it's the material, its configuration, it's environment, etc. But this reminds me of a bit of advice I once got from an oracle of prewar Packards when inquiring about the double-pinstriping on my 34 Eight, and it applies as well to (1) painting things like brake drums and radiators, and (2) thinking about that last slice of pizza:

"Think Thin".

Guscha wrote:
Quote:

Gerd,

Your statement would be true if the black paint absorbs infra-red, but I am not sure the pigments actually absorb much in that part of the spectrum. Black absorbs visible light very well (the entire spectrum), and thus heats up. So, I think, the paint will primarily be an insulator relative to heat transfer from inner to outer surfaces; unless the coating has a very high content of a metal that with greater heat conductance that the aluminum (as you stated).

Dave, I am relying on my not so great memory of pigment chemistry, so please correct me if I am wrong.

Edit: Pigments do absorb in the infra-red, but probably not enough to overcome the insulating effect of the resin matrix they are suspended in. An old article on infra-red spectroscopy for identifying inorganic pigments is here:

pubs.acs.org/doi/abs/10.1021/ac50164a025

Gerd, okay let us have another go at it without mentioning the "t" word. Does the paint color make any difference in heat dissipation? Is this what you wanted?

Quote:

I think the conclusion, from this thread, would be measurably no. The metal casing would dominate the thermal relationship.

One of my other hobbys is diesel trucks, as seen in my sig, and with very powerful engines in our trucks, automatic transmission heat is always a problem. Performance tranny pans for heavy duty use are FINNED UNPAINTED ALUMINUM. These pans are usually oversized to hold more fluid. More fluid means that the fluid can stay in the pan longer, away from the heat for added cooling.