Don’t install a trans/DCT cooler in your E8x/E9x BMW without doing this!

BMW N54 vehicles: Replacing the stock transmission heat exchanger with an aftermarket transmission or DCT cooler seems like it should improve engine cooling performance because the engine coolant won’t need to cool the transmission fluid, but you will lose 15% of your radiator capacity if you don’t modify your “auto” radiator or replace it with a “manual” radiator. This applies to the e82/e88 135i, e82 1M, e89 Z4 35i & e90/e91/e92/e93 335i vehicles with the N54 engine.