Any truth to this "Theory"?

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May 9, 2003
Fayetteville, NC
Read this in another forum as an explanation for failure in trannys when the fluid is changed/flushed after a long time; Can this be the reason? QUOTE: "...What usually happens, more or less, as the clutches wear, you'll get microscopic particles in the fluid that almost act like a friction modifier( if you will) that still works with the rest of the hydrolic system that still exists, (god my spelling s***s). It will eventually get to the point were it will start to clog (the system) up. It has been said (in the old days ) that when you change the fluid after an extended period of time without service (shiftes OK but fluid looks like s**t), you start to have problems because you lost all of the "MODIFIER" from the old fluid, which were the "shavings" from the clutches. You still should never see metal in your fluid when you check it. Maybe in the pan win it is dropped. I have had this happen to me in the past with an old Turbo 350 in my '70 MonteCarlo. It was shifting a little sluggish, so I changed the fluid in my drive way and it was never the same after that. I'm not saying this is your case, just thought I'd pass on a little personel experiance..."
I don't know of the validity of the theory for the "truth" of it ...and I've never experienced it myself...but others have alleged that, at some point, flushing a trans is unwise. Sounds like the theory is can I say this (old timer thingy - and try and integrate what I'm saying here as it applies to the "theory") adding Type F fluid to a GM trans works ..but you get harsher shifts due to the added friction material that Ford units needed. Back then ..some trans shops just had one ATF ..Type F. This was the folly of TrickShift® when it first came out. It had TONS of friction additives that made your auto a snap shifter also disintegrated most of your hard parts as well. So it may have some merit ...
Changing tranny fluid does not make transmissions fail because of a change in the friction coefficient of the fluid. It makes them fail because it washes out the sludge which is allowing worn internal seals to continue to seal long after they would have normally failed. Of course, if this is true, the unit has been either abused or is long overdue for a rebuild anyway. There is no good that comes from having particles circulate in an automatic. They destroy bearings and bushings and clog the bores in the valve body. Fortunately, most of it falls out of suspension when it cycles through the pan.
I think TooManyWheels is right on the money. The way I think about it (and I got this from a professional trans rebuilder) is that if the trans is at the point where it fails due to a fluid change, it would have failed anyway, you just sped up the process with a fluid change. So I would say if the fluid is super nasty and way beyond the change interval, just leave it in and drive 'till it starts to malfunction, given that you're going to need to rebuild it anyway. Obviously the best thing is to change the fluid on schedule in the first place.
I think this is an old automotive myth. If your tranny is in good working order or even neglected a bit, fresh fluid will do no harm at all. I have chnaged out factory tranny fluid at 100k in the past with no problems. It was a nasty brown color and smelled real bad. I think this whole myth is due to people who change their tranny fluid once they are already experiencing problems. Obviously, the new fluid in not going to cure the problem. Once the tranny goes altogether, these people then blame the new fluid instead of themselves.
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