transurgeon :chips'nflakes in 4L60E filter

Could you explain the oil px and circulation system of the 4L60E? I have just examined the 4th filter (drained pan change filter every 25000 Kilometers) and have noted very minor metal flaking and a brittle dark brown
coloured material trapped in the filters. I am questioning the source of the brittle material as I have seen it in each filter removed. Irregular shape glossy smooth surfface one side and rough texture on other side A little history: Trans rebuilt 100000 Km ago after hard 1-2 shift, sloppy 2-3 and a slipping tq converter. Its from a '93 k1500 Suburban (OBD1) so no p1870 codes. Have not had any ses lights so no codes to pull. No shifting issues either. Trans temp while towing up 30Km/7%grade reached 255* in second gear holding steady @ 70 Km/hr (2 external coolers only) Thanks in advance Rolf
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Picture of flakes posted
alt.binaries.pictures.autos.4x4
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Gary Here is the link to picture of the chips'nflake... your thoughts please
http://pic19.picturetrail.com/VOL1042/3911395/8088476/107352289.jpg

brown
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how is the transmission shifting and working,the most likely cause of the chips is the paint from the dipstick tube,simple look at the dipstick tube and see if black paint is coming off of the tube. if it is i would change the tube and reservice the trans,might even flush the trans.
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"Rolf" wrote:

dark
from
Breifly 255 to TOO HOT. You should never tow (or even operate) at that temp. At 220 or so throttle back some and at or above 230 it is time to shut it down (idle for a while to cool off). Also though some will say otherwise, you ALWAYS run fluid thru tank cooler first then aux cooler because the tank cooler can knock the fluid down below 200 degrees quickly and then the aux cooler can cool it more. Even 160 to 180 degree water can cool oil a good bit if it is hot before it is sent to aux cooler for additional cooling. Air coolers only should never be used as a only cooler and if you lose air flow you can toast tranny quickly. My guess here is that clutch fan was not engaged much and the aux coolers did little to cool tranny. One more tip, stay above 2500 RPM or more when pulling hard because at that RPM and above converter clutch locked or not you will be fully off the heat producing stall of the converter.
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