Re: Transmission Cooler Mounting FAQS
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Re: Transmission Cooler Mounting FAQS



On Sat, 25 Jun 2005, Bruce Hevner wrote:

The auto trans gives off more heat than you think. Anyway that's my story
and I'm stiiicckken to it.


Yeah, check this out!

The efficiency of an automatic transmission is pretty good;
somewhere in the upper 90's percentage-wise.

Horsepower NOT sent to the wheels becomes heat.


It's about 770 watts per horsepower if I recall. Here's chart showing how much heat is produced:


transmission efficiency HP | 0.99 (1%) 0.98 (2%) 0.95 (5%)
------------------------------------
100 | 770 1540 3850 watts of heat
200 | 1540 3080 7700
300 | 2310 4620 11550
400 | 3080 6160 15400



As HP passes through the trans, 1% to 5% (anyone know numbers?) of it turns to heat. 100HP engine power generates 770 watts of transmission heat.

Put a 750 watt spaceheater inside a small metal enclosed box and
see how hot it gets. If there wasn't a safety switch, it would
reach 500, 600, 700 degrees in minutes. The spinning torque
converter dumps some heat, as does the cast body, the rest depends
on that cooler.

It's a miracle that auto transmissions work at all!

(Even a little Rambler with 100hp six doesn't really output 100hp
for very long, at highway cruise, it's what, 30? 40? hp? The
problem is the heat builds up in the transmission, even a 300 -
400 watt space heater locked in a metal box will get oven-hot.)

You could probably work out the difference in miles/gallon manual
vs. auto trans in terms of BTUs/mile and figure out the amount of
heat produced in the automatic transmission that way.







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