Very cool build I think that standalone trans cooler will help. I was surprised the p71 got a separate power steering cooler. Yet kept the standard production trans condenser setup. I agree it does not seem like you're trying to run down on purpose. If the pressure changed with the cooler you could likely adjust that with a tune. Could probably alter the function of the od button as well. Have it still lockup but not shift into od when off then normal when on. That way you'd still be keeping od from engaging. Yet trans temps would drop + less power loss due to the mechanical connection.
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2008 Ford Crown Victoria Police Interceptor P71 with street appearance package.