Originally Posted by ferny
question for those of you that went with the small filter method. I routed mine into the engine bay and the other day i noticed that the filter looked like it was soaked in fluid (diff fluid im assuming). Anybody have this issue?
edit: pic for reference
I've read through this thread back to the original post in 08 or whatever. And what you are describing was something I was curious about.
That check valve or one way breather on the rear diff allows for a slower equalization in the diff, correct? (If air goes out, air has to come back in or else the diff would implode eventually, so the valve must provide some slow breathing back into the diff.) When the atmosphere inside the diff gets heated up it can burp out that valve, and that valve allows for a slower return to "normal" pressure inside the diff once the truck is stopped. This makes me think the rear diff is engineered to operate under a higher pressure, since the temperatures don't equalize as rapidly. Now, if you remove that one way valve and replace it with a two way breather type deal, like a fuel filter or just open, you are allowing a more rapid equalization of pressure to occur. So, whatever pressure that one way valve was designed to contain now goes shooting up that tube and escaping easily into the outside atmosphere, taking some fluid with it. The shorter the tube you install, the less travel, so the greater the chance of fluid escaping over time? I dunno, but seems to me like an engineered one way valve replaced with a two way is significantly altering how the thing is designed to operate.