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Old 10-21-2019, 12:00 PM   #1 (permalink)
Master EcoModder
Join Date: Jul 2017
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Trans cooler lines too big?

Somehow I accidentally kinked one of me OEM transmission cooling lines on my 05 Civic. No idea how that happened, my best guess is it happened when I changed the trans. So far the kink is not causing any problems, everything is operating correctly and the trans is running nice and cool with my aftermarket cooler. However, the kink obviously can’t be good, so I am going to replace those lines.

I would rather use braided stainless AN hoses all the way to my cooler than those OEM metal lines and rubber hoses because IMO they look much better and may be more reliable. I was initially going to go with 8AN lines (1/2 inch) rather than the stock 3/8 inch lines since the price difference is negligible and I figure less restriction could never hurt. In my mind, even if flow doesn’t increase, the pump won’t have to work as hard to circulate the fluid through the larger lines, possibly extending its life, reducing fluid temps, and slightly improving efficiency by reducing the power required to run the pump.

However, I have read that using cooler lines that are too large can actually be a bad thing because they may flow too well and will cause lower line pressure in the trans making it shift softer, which I certainly don’t want since I did mods to raise the line pressure since I like firm shifts.

So my question if restriction in the cooler lines is actually desirable. I don’t see how restricting the flow could ever be a benefit, but I just want to be sure that I am not going to cause a problem by installing larger lines. Thank you very much in advance!

Last edited by EcoCivic; 10-21-2019 at 09:39 PM..
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