According to Abe Khalil and John Eleftherakis, two engineer/tribologists who have been studying automatic transmissions and ATF since the '80s, 75 percent of the harmful debris generated in an automatic over its operating life comes from the manufacturing process and break in. After sampling the oil in thousands of automatics in service, they found that the average trans with 70K or more miles that has not had a service contains approximately 263 mg/l (milligrams per liter) of contaminants, 90 percent of which is metallic. Of those metallic particles, 51 percent are ferrous (iron/steel), 21 percent copper, 11 percent aluminum and 7 percent lead. The particles range in size from 5 to 80 microns, about 82 percent of them larger than 5 microns. Yes the trans has a filter, but the best on the market today filters at 80 microns nominal and many cheap ones, or older filters are at 100 microns, or larger. Some of the screens in older transmissions are 150-200 microns and all they get are the "boulders.
Long term, the metallic particles cause wear on the pump vanes/housing and on bearings and bushings, but valves don't like debris either and that's where the shorter term problems can come from. A chunk of debris can score the bore of a valve and cause it to leak, or jam outright. I don't have to tell you what a metallic particle will do to a rubber seal or o-ring. With the advent of electronic valves, a new problem was created. What is an electronically controlled valve?? An electromagnet! Magnets attract ferrous particles, so the iron in the trans is gravitating to those areas and causing valve malfunctions to occur even sooner. Once the valves start to malfunction, you get reduced pressures or delayed shifts, all of which cause extra wear on the clutches. Often it's so slow and imperceptible that the driver doesn't feel it until it gets really bad. That might be at 100K miles, so he says, "Oh well" and has the trans rebuilt when with some care, that trans might have outlasted the car. Sometimes there is so much manufacturing grunge (or remanufacturing... rebuilt trans have the same trouble) in the trans that it fails under warranty (very common).
Thing is, if you can keep the contaminants under control, either by changing the oil or improved external filtration (the internal filters are low efficiency) you can greatly extend the reliability of the trans and the life of the oil. I interviewed Abe Khalil for a project and he said the first thing he does with a new car of his own is change the trans oil and filter (within about 5K miles). According to him, that eliminates 90 percent of the potential problems down the road.
A normal UOA is not a great way to measure contaminants in an automatic overall because the spectrometer used to test for metals only "sees" the particles under about 5 microns. The insolubles is merely a conglomeration of the stuff that settles out in a centrifuge. Both of these results can be reasonably accurately interpreted by a skilled and experienced person well enough to make some recommendations but it's still a "blurry snapshot" at best. Better to have a particle count done if you really need to know... but when Blackstone recommends an oil change, take heed. To clarify, I don't recommend the exgtra-cost particle count route unless you are especially pedantic or deep in knowledge-seeking mode. A UOA, interpreted by a pro, is usually sufficient.
Let's go back to the 75 percent thing above. Once the initial break-in has occurred, the transmission's internal production of contaminants (wear particles) slows way down in most cases, so the followup oil changes can be lots longer. The exceptions could be particularly hard worked units or those where the oil has been allowed to break down from age or stress and wear increases from lack of lubrication.
I'll still get on my soapbox here and shill for external filtration. A simple cooler line filter (google Magnefine as one easy example) can extend trans oil life as well as trans life itself. Abe Khalil quoted me a generic optimal ISO cleanliness code for ATF (that's a number you'd need to get from a particle count) of 16 (I'll leave it to you to research the two and three digit ISO codes if you don't understand the reference). It's achievable easily by external filtration or by oil changes, but to maintain that level of cleanliness without filtration it might require dumping oil that's essentially in good shape but for a high level of contamination. Remember that every ISO code number jump is up to a 50% increase in the level of contamination.
How quickly an AT dirties it's oil in normal use to the 19/16 level, after the beak-in process is complete, is highly variable according to the unit.
So, bottom line: For optimal trans life, either add an external filter right away or change the oil within about 5K miles. Updated info on the 5K stat would be that the AT mfrs. have really cleaned up the manufacturing process in the past few years and eliminated a lot of that built-in grunge. You still have break-in to contend with but I am told even that has improved. I haven't talked to Khalil in a few years and don't know what he would say right this minute, so I am sticking with 5K as a "perfect world" recommendation for those like me who are pedantic. Bet-hedgers... try about 15K, then do 60-80K intervals after (or according to h OEM or if in severe service). Overall, an external filter, well and correctly installed, hit's all the bases and allows you to run the factory fill for what is essentially a "full" OCI safe from high contaminant levels. You can then base the OCI on oil condition rather than contaminant level (and those are really best viewed as two separate categories).
Long term, the metallic particles cause wear on the pump vanes/housing and on bearings and bushings, but valves don't like debris either and that's where the shorter term problems can come from. A chunk of debris can score the bore of a valve and cause it to leak, or jam outright. I don't have to tell you what a metallic particle will do to a rubber seal or o-ring. With the advent of electronic valves, a new problem was created. What is an electronically controlled valve?? An electromagnet! Magnets attract ferrous particles, so the iron in the trans is gravitating to those areas and causing valve malfunctions to occur even sooner. Once the valves start to malfunction, you get reduced pressures or delayed shifts, all of which cause extra wear on the clutches. Often it's so slow and imperceptible that the driver doesn't feel it until it gets really bad. That might be at 100K miles, so he says, "Oh well" and has the trans rebuilt when with some care, that trans might have outlasted the car. Sometimes there is so much manufacturing grunge (or remanufacturing... rebuilt trans have the same trouble) in the trans that it fails under warranty (very common).
Thing is, if you can keep the contaminants under control, either by changing the oil or improved external filtration (the internal filters are low efficiency) you can greatly extend the reliability of the trans and the life of the oil. I interviewed Abe Khalil for a project and he said the first thing he does with a new car of his own is change the trans oil and filter (within about 5K miles). According to him, that eliminates 90 percent of the potential problems down the road.
A normal UOA is not a great way to measure contaminants in an automatic overall because the spectrometer used to test for metals only "sees" the particles under about 5 microns. The insolubles is merely a conglomeration of the stuff that settles out in a centrifuge. Both of these results can be reasonably accurately interpreted by a skilled and experienced person well enough to make some recommendations but it's still a "blurry snapshot" at best. Better to have a particle count done if you really need to know... but when Blackstone recommends an oil change, take heed. To clarify, I don't recommend the exgtra-cost particle count route unless you are especially pedantic or deep in knowledge-seeking mode. A UOA, interpreted by a pro, is usually sufficient.
Let's go back to the 75 percent thing above. Once the initial break-in has occurred, the transmission's internal production of contaminants (wear particles) slows way down in most cases, so the followup oil changes can be lots longer. The exceptions could be particularly hard worked units or those where the oil has been allowed to break down from age or stress and wear increases from lack of lubrication.
I'll still get on my soapbox here and shill for external filtration. A simple cooler line filter (google Magnefine as one easy example) can extend trans oil life as well as trans life itself. Abe Khalil quoted me a generic optimal ISO cleanliness code for ATF (that's a number you'd need to get from a particle count) of 16 (I'll leave it to you to research the two and three digit ISO codes if you don't understand the reference). It's achievable easily by external filtration or by oil changes, but to maintain that level of cleanliness without filtration it might require dumping oil that's essentially in good shape but for a high level of contamination. Remember that every ISO code number jump is up to a 50% increase in the level of contamination.
How quickly an AT dirties it's oil in normal use to the 19/16 level, after the beak-in process is complete, is highly variable according to the unit.
So, bottom line: For optimal trans life, either add an external filter right away or change the oil within about 5K miles. Updated info on the 5K stat would be that the AT mfrs. have really cleaned up the manufacturing process in the past few years and eliminated a lot of that built-in grunge. You still have break-in to contend with but I am told even that has improved. I haven't talked to Khalil in a few years and don't know what he would say right this minute, so I am sticking with 5K as a "perfect world" recommendation for those like me who are pedantic. Bet-hedgers... try about 15K, then do 60-80K intervals after (or according to h OEM or if in severe service). Overall, an external filter, well and correctly installed, hit's all the bases and allows you to run the factory fill for what is essentially a "full" OCI safe from high contaminant levels. You can then base the OCI on oil condition rather than contaminant level (and those are really best viewed as two separate categories).
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