Surface temperature of Aluminum cast gearbox

Joined
Jun 14, 2011
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Denmark, Europe
Hi, I am going to paint my cast aluminum gearbox and transfer box (both with cast heavy cooling ribs) both installed in my 4WD. They are both manual. Does anyone know the surface temperature of the cast aluminum under normal operation? For instance is it below or above 212 degF ... or maybe somebody has some more precise figures? Thanks, Lucas
 
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Mar 8, 2012
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MO
Should be well below 212. Why paint the aluminum? You may lose some cooling capacity.
 

djb

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Jan 16, 2006
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Los Gatos CA
Black paint (to be more precise, paint that is 'black' for IR radiation) will radiate heat more effectively, but most of the heat transfer will be conduction/convection. So paint it whatever color you like. Except pink or purple. Those colors won't work.
 
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IR guns on hot highly reflective metal can be very inaccurate. Try painting a small spot and then comparing IR readings on that spot and the shiny metal.
 
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I think the only time you'd have trouble with MTX temps is long long grades with lower speeds. Or if you are using your truck like a tractor, transmitting lots of hp with little air flow for a sustained period.
 
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Oct 10, 2008
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Sunny Florida
Originally Posted By: HangFire
IR guns on hot highly reflective metal can be very inaccurate. Try painting a small spot and then comparing IR readings on that spot and the shiny metal.
So true. I was mystified when I could not get accurate readings on my new fleet truck's trans pan. It was too shiny. Our older trucks give easy accurate readings after the finish dulls out a bit. To the OP's original question about temps, I have gotten temps of nearly 300 degrees at the track in a relatively low hp car (~300hp) in a 5 speed tremec. I'm not sure how that relates to a 4X4, but I am sure if you have huge tires and are going high speed down the highway you could easily exceed 212...
 
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Oct 2, 2008
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Flatlands of Indiana
Originally Posted By: SteveSRT8
Originally Posted By: HangFire
IR guns on hot highly reflective metal can be very inaccurate. Try painting a small spot and then comparing IR readings on that spot and the shiny metal.
So true. I was mystified when I could not get accurate readings on my new fleet truck's trans pan. It was too shiny. Our older trucks give easy accurate readings after the finish dulls out a bit. To the OP's original question about temps, I have gotten temps of nearly 300 degrees at the track in a relatively low hp car (~300hp) in a 5 speed tremec. I'm not sure how that relates to a 4X4, but I am sure if you have huge tires and are going high speed down the highway you could easily exceed 212...
This is due to the emissivity of the surface. Sore IR guns allow you to change the base setting to match the surface you are measuring. shoot some flat black on it to flatten the surface sheen. You can actually use some spray anti-perspirants to temporarily flatten the surface.
 
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