Just did 4.8is transmission oil pan drop and filter.

[JCL]

Originally Posted by TiAgX5

Yeah, the "sealed" statement is a common misconception.

The trans vents to the atmosphere thru a large tube.


This thread came to a halt when I brought it up...........

http://www.xoutpost.com/bmw-sav-foru...service-4.html

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.

[upallnight]

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.

It maybe sealed from outside contaminants, but what about the contaminants that are produce by the trans as it being operated? All manufacturers use filters and magnets to prevent some of the contaminates from circulating within the trans, but the ATF does get contaminated.

[JCL]

We may still be arguing semantics, but I don't think of the natural wear products within the transmission as contaminants. They are designed to be in there. The fluid doesn't get chemically changed, for example, like engine oil does. It certainly does get thicker due to clutch wear material, but fortunately the transmission adapts to that viscosity change, by design. It works fine until the filter is clogged and pressures drop. As we have seen, though, it can go hundreds of thousands of miles without that happening.

I would say the most common source of contamination is the fill plug, when owners introduce non-spec fluids.

[RRPhil]

The breather on a 5HP24 looks like this.



The breather tube that runs up & over the valve cover is for the front differential.

Could someone explain to me how you overfill a transmission that’s fitted with a combined filler/level plug?

Phil

[upallnight]

Originally Posted by RRPhil

The breather on a 5HP24 looks like this.



The breather tube that runs up & over the valve cover is for the front differential.

Could someone explain to me how you overfill a transmission that’s fitted with a combined filler/level plug?

Phil

Since ATF expands with heat and if the ATF fluid is below the recommended temp for the check level, you can overfill the trans by adding fluid to the trans before it reaches the temp that it needs to be in order to perform a accurate check of the fluid level.

[RRPhil]

The engine would have to be running to have a chance of overfilling (because the torque converter and valve block drain down) and the transmission bulk oil temperature increases at around 5 deg.C. per minute with the engine running.



So say ambient temperature was 10 deg. C. (would anybody try checking their fluid level at a temperature below this?) and it took a minimum of one minute to carry out the check. So that’s a temperature error of 20 deg.C. The volumetric coefficient of expansion will be around 0.0007/deg.C for ATF so that represents 0.13 litres. The throat area of the sump at the filler plug (including deducting the valve block) is around 375cm2 so that represents less than 4mm in fluid level.

My point is, you’d have to try really hard to overfill a 5HP24

Phil

[upallnight]

Originally Posted by JCL

We may still be arguing semantics, but I don't think of the natural wear products within the transmission as contaminants. They are designed to be in there. The fluid doesn't get chemically changed, for example, like engine oil does. It certainly does get thicker due to clutch wear material, but fortunately the transmission adapts to that viscosity change, by design. It works fine until the filter is clogged and pressures drop. As we have seen, though, it can go hundreds of thousands of miles without that happening.

I would say the most common source of contamination is the fill plug, when owners introduce non-spec fluids.

Well I consider anything that wasn't a part of the original mixture as contaminants. If it doesn't contaminate the fluid why bother to have a filter and magnets in the trans?

[JCL]

Originally Posted by upallnight

Well I consider anything that wasn't a part of the original mixture as contaminants. If it doesn't contaminate the fluid why bother to have a filter and magnets in the trans?

Fair enough.

Only my opinion, but I would say to keep it out of the valve body. Not because it is changing the functional properties of the fluid in a meaningful way.

[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).