FYI Some good Transmission tips

[JCL]

Ghost-Flame:

The following will explain the background on adaptive transmission shifts. These are BMW training materials that cover this. Essentially, when automatic transmissions became electronic, manufacturers gained control over shifting, and then in a further development, gained the ability to measure shift performance, and adapt clutch pressures based on shift times. They measure slip (difference between input and output speeds) and adjust for clutch wear, among other things. That is what gets invalidated when the fluid is changed, as the transmission has stored the expected shift characteristics. Your transmission shop will know the importance of clearing those adaptations with a computer diagnostic tool when they change fluids on a BMW (and the same applies to many other makes of vehicle). The following are BMW materials, so they apply to both the GM and ZF transmissions. They are worth reading through, IMO.

Transmission Fundamentals Part 1

Transmission Fundamentals Parts 2

Electronic Transmission Control Part 1

Electronic Transmission Control Part 2

[JCL]

Originally Posted by Ghost-Flame

I clearly don't understand. If particulates are held in suspension how can sludge build up? If particulates are held in suspension then why am I not flushing them out when I drain and fill? If particulates are held in suspension then abrasives are constantly wearing on your mating surfaces with never a break, how can that be better than new fluid?

100,000 miles is the life of the transmission after it has been prematurely chewed up by dirty, micro gritty atf,that is left in by the Motor Werks. They like... no love... to take your 6,000 clams when THEIR dirty atf has ruiend the transmission before its time. when atf changes could have prolonged trans failure and the extraction of said $6000.

If the above old fluid theory was true then ... I don't know do I?

PS I have the next 33 bottles of atf ageing on a shelf in my garage... I rotate it and turn it every month... Orson Wells checks in occasionly to see what's up.

The particulates that are held in suspension are not significantly abrasive. They are predominantly friction plate material. If they were abrasive, then your shifts would not be very smooth. They provide colour to the fluid, but do not change the fluid friction properties. They do change the viscosity, and the transmission adjusts for that within a predetermined range.

The sludge in the bottom of the pan is the stuff that didn't go through the strainer at the oil pickup (prior to the filter). It just sits in the pan, and doesn't hurt anything. It is on the dirty side of the filter, not the clean side. It does start to hurt things when it accumulates to the point where it blocks the filter.

The screen and filter are designed to separate out the particles that are large enough to do damage. That is why you want to use an OE filter, so that you don't buy a filter that has a larger micron rating that lets larger particles through. The ones that pass through the OE filter are of a size that they aren't considered critical. There aren't gritty metal particles circulating through the filter and abrading bearing surfaces. That is an exageration.

All that said, nothing is absolute, and that is why particles in suspension can get trapped in small passageways. There is not a significant flow through those passageways, they are more like dead ends. Over a long period of time, particles can collect there. Such is life.

I think you are considering the transmission fluid as primarily a lubricant. While it has that function, it is not a demanding lubrication requirement IMO, and the transmission fluid has many other functions. It is predominantly a heat exchanging medium, and it needs to be non-compressible as it is a hydraulic fluid. The lubrication function is so low on the requirements list that Dexron ATF, a 10 weight straight-grade mineral oil with few lubricating additives, can function for 200,000 miles while not breaking down. This isn't an engine, with high lubricating demands.

Hope some of that helps. I am not trying to change your mind on whether you should change your ATF, you have already made that decision and your inventory alone suggests you will keep changing it. Let me know what you think of the training materials I posted above.

[bigwave2255]

huh, i always thought i was doing the right thing by changing into neutral when stationary in stop start driving, however after reading through the above links it seems that if one is in stop start driving the trans adapts and stays in second gear, unless speed goes over 40 mph or the trans is shifter to sport or NEUTRAL.

i always thought i was doing the right thing by easing the load on the torque converter and that in tern would keep heat down.

i going to have to re-evaluate this in light of the above

[JCL]

At idle there is no significant load on the torque converter, so changing it into neutral won't make a difference, apart from wearing out the linkage earlier. If you are stopped for more than 15 seconds, it makes more sense to turn the engine off, as that will reduce wear and save fuel (assuming you are in a location where that is safe to do so).

[bsprtsgrp]

I just called ZF USA in IL. and spoke with a technician there regarding this very issue. Just a note: I actually called them prior to reading this thread as I was contemplating doing a tranny fluid change and wanted to get the manufacturers recommendation first.

His recommendation regarding this topic (at my 75k mileage) was "the transmission should be serviced". I asked him about BMW's Lifetime fluid statement and he said it's more about BMW's "Maintenence Free" marketing than anything else. He said if the fluid is not discolored and does not smell burnt or has excessive sediment then there is no harm in a drain/filter/and re-fill. He did recommend staying with Esso(Mobil) 71141 or ZF Lifeguard #5

He said if the fluid is dark and smells, then there are other issues with the transmission going on.

Just thought I'd pass this on....

[HPIA4v2]

Originally Posted by bsprtsgrp

I just called ZF USA in IL. and spoke with a technician there regarding this very issue. Just a note: I actually called them prior to reading this thread as I was contemplating doing a tranny fluid change and wanted to get the manufacturers recommendation first.

His recommendation regarding this topic (at my 75k mileage) was "the transmission should be serviced". I asked him about BMW's Lifetime fluid statement and he said it's more about BMW's "Maintenence Free" marketing than anything else. He said if the fluid is not discolored and does not smell burnt or has excessive sediment then there is no harm in a drain/filter/and re-fill. He did recommend staying with Esso(Mobil) 71141 or ZF Lifeguard #5

He said if the fluid is dark and smells, then there are other issues with the transmission going on.

Just thought I'd pass this on....

Just an observation, I just did another drain/fill on my trans last weekend @76kmiles (2002 ZF trans). this time I noticed the coloration is more of thick Chinese tea; while at 42kmiles (drop the pan and filter) the color was more like Coca-cola and metal shaving suspended, you can search my post on that one.

From this experience, I believe if you want to flush the fluid do it early w/ filter and forget the second time around altogether (it's diminishing return IMHO).

I am planning doing it on my 535i 6-sp ZF trans next month @35K on the odometer and maybe never have to do it again until I sell the car.

TRemember there is a California store that carries ZF-5 and ZF-6 fluid so no guessing game no more(The CTSC - ZF Parts), if you want to do it do it right.

[Ghost-Flame]

Originally Posted by JCL

Ghost-Flame:

The following will explain the background on adaptive transmission shifts. These are BMW training materials that cover this. Essentially, when automatic transmissions became electronic, manufacturers gained control over shifting, and then in a further development, gained the ability to measure shift performance, and adapt clutch pressures based on shift times. They measure slip (difference between input and output speeds) and adjust for clutch wear, among other things. That is what gets invalidated when the fluid is changed, as the transmission has stored the expected shift characteristics. Your transmission shop will know the importance of clearing those adaptations with a computer diagnostic tool when they change fluids on a BMW (and the same applies to many other makes of vehicle). The following are BMW materials, so they apply to both the GM and ZF transmissions. They are worth reading through, IMO.

Transmission Fundamentals Part 1

Transmission Fundamentals Parts 2

Electronic Transmission Control Part 1

Electronic Transmission Control Part 2

Thanks for the training materials, I love to read that stuff! I have scanned them quickly this morning but, will read them thoroughly later when I have time. Maybe I'll change my mind.

[Ghost-Flame]

Originally Posted by HPIA4v2

Just an observation, I just did another drain/fill on my trans last weekend @76kmiles (2002 ZF trans). this time I noticed the coloration is more of thick Chinese tea; while at 42kmiles (drop the pan and filter) the color was more like Coca-cola and metal shaving suspended, you can search my post on that one.

From this experience, I believe if you want to flush the fluid do it early w/ filter and forget the second time around altogether (it's diminishing return IMHO).

I am planning doing it on my 535i 6-sp ZF trans next month @35K on the odometer and maybe never have to do it again until I sell the car.

TRemember there is a California store that carries ZF-5 and ZF-6 fluid so no guessing game no more(The CTSC - ZF Parts), if you want to do it do it right.

Your opinion is based on research, I respect that. Mine is based on 3 generations of shade tree mechanics and what other manufacturers still recommending a change interval. That does not make me right, I guess I could be wrong. It just works against my sense of logic and it makes me feel bad. Who wants to feel bad?

What of the heat related properties of fresh trans fluid vs old trans fluid? I was always told that fresh atf helps keep the trans cooler; that may not be a benefit in these transmissions. you and a lot of others are apparently having great success leaving the trans fluid in, that's worth considering and it's interesting and it flies in the face of my logic.

I'm exhausted, I'm done

Now can you and JCL check my thread on removing the trans and tell me what you know? I promise I won't argue

[HPIA4v2]

Originally Posted by Ghost-Flame

Your opinion is based on research, I respect that. Mine is based on 3 generations of shade tree mechanics and what other manufacturers still recommending a change interval. That does not make me right, I guess I could be wrong. It just works against my sense of logic and it makes me feel bad. Who wants to feel bad?

What of the heat related properties of fresh trans fluid vs old trans fluid? I was always told that fresh atf helps keep the trans cooler; that may not be a benefit in these transmissions. you and a lot of others are apparently having great success leaving the trans fluid in, that's worth considering and it's interesting and it flies in the face of my logic.

I'm exhausted, I'm done

Now can you and JCL check my thread on removing the trans and tell me what you know? I promise I won't argue

Ghost, I know removing trans is beyond my ability (that's why I decide to flush my trans in hope it'll never come to that).

Hope Swiss-Frank can chime in, or you can PM people who posted on trans rebuild before. GL.