Just did 4.8is transmission oil pan drop and filter.

[TiAgX5]

Originally Posted by JCL

That is because it had devolved into a semantic discussion of what the word sealed means. It is vented to atmosphere, agreed. If you ford a river that is deep enough you could get water in it. I suppose. Not sure how water would be drawn in though, or if the electronics would still be functioning in water that deep.

In the thread you mention, you suggested that contaminants and so on could enter and degrade the trans fluid. You claimed the fluid became corrosive over time. That is similar in concept to engine sumps which get contaminated by by-products of combustion and fuel dilution. That ain't gonna happen. That is the reason it is referred to as sealed.

So, if you like, it is sealed from the contaminants which typically degrade other fluid compartments.

Lets look at the "semantics" of BMWs definition per their tech data.

http://www.bmwtech.ru/pdf/e46/ST034/...20Internet.pdf

Page 4 states "Transmission fluid is designated as "sealed for life".

I define that as a system that's not user friendly in regard to checking fluid level/adding fluid. BMW uses the "sealed for life" definition to explain to owners that fluid level needs to be checked in a service shop, on a lift/over oil change pit, with tools and temp sensor (and the chance for a tech to get in/under the vehicle to inspect for any needed repairs on the ENTIRE vehicle, cha-ching!).

As I stated in the other trans thread, the system would require a diaphragm seal to qualify as a "sealed system".

Even 2 one way ball check valves (one for venting positive pressure, one for equalizing negative pressure, with a filter element), would significantly reduce any chance of envornmental contaminants/moisture from entering the system.

I've seen significant dirt, dust, grime, road salts, grass/leaf/bug materals under the plastic engine covers on BMWs (where the tube vents).

Not sure of % of fluid PH change over years of driving/mileage, I'm sure it's measureable and considered "acceptable" by BMW (the same BMW that gets paid when MANY trans fail, and where I was told "lifetime" is in excess of 100k miles).