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Shelburne Ontario Canada | So, read thru all replys, this will take awhile, but i was explained by a man i trust. ATF is extremely slippery oil even under very hi pressure and temp.
All electro shifting trannys self learn , to pressure, eng load , rpm, length of time from shift to eng load applied, it takes that data and changes all those perimeters constantly.
So as oil brakes down it gets less "slippery" for lack of a big word, yes valve can at that point get gummed from dark sludge type stuff, and valving shift values get very lazy, as oil isnt slippery do clutch grab at a much faster lockup factor than new slippery oil.
So the learn factor has evaluted shifts from the last 50,000-150,000.
Now u drop all oil, flush torque convertor, cooler and all. You go from a black thick , gritty type of poor crap , almost abrasive between figures wen u feel with fingers, now its pure slippery, quick thin new piss , pressure readings change,
clutch engagement at factory was say 0.65milli volts to engage clutch to full shifted power eng solid with ground, now with black sludge its down to 0.25 mili volts and grabs solid. Now u go instantedly form sludge to slippery new, and no 50,000 shifts to slowly relearn the milli volts, so techinacally the first 500 shift the clutch is only half engaging. That is why they all blow up after a flush. If you do flush. Drive extremely carefull for first 1000, let it relearn.
Or do as he recommended, in my stuff, pans with no drain i pop most bolts, let out wat ever flows out, did wifes 1500 chev this morn. Was 5 quarts came out . Snugged pan back on , dumped 5 oil in , take it for a nice coffee run an all good.
On my 2018 chev traverse, 2018 chev1500, even my 2500 duramax, i was shocked how black the tranny oil was at 50,000km, yes was still purple redish, but the new is pure red,
in allison i drop the oil pan drain plug , swap that oil every 25,000, actually stays very good that way. Just gets a bit dark. At 50,000 i do spin on filter, 200,000 i do the inside filter, but then again only change the oil in the pan. After an easy coffee run ur good to go.
The worst i had was the traverse, at 50 that oil was so black u would think it was used eng oil. I really question the quality of factory fill oil. Transfer case and transaxle gearlube was all just pitch black and stinky at 50000. I have done changes since and its much cleaner.
Did tranny 4 quart changes on traverse trans at 50, 60, and 70. Now almost 150 and doing it at 25000. Its a bit dark but much better.
My old truck went to 600,000 , had power chip and drove like i stole it, was still decent wen it left rottin.
Hopefully that helps clear up some of the questions. Sorry for the long read.
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Changing automatic transmission fluid in car
