Quote:
Originally Posted by Gregski
Hatzie you know too much, fortunately I know nothing so we cancel each other out. My fridge magnet seemed to be clicking on to shavings still so that's a good sign, LOL !
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The only reason I know about the frige magnets is GM quietly released a service bulletin for the fragile 4T65E-HD in my LS4 Impala.
Among the transmissions listed besides my 4T65E is the 4L80E, 4L60E, & 4L65E.
I read some about what happens to magnets when they are run at temps just slightly beyond their happy zone. I knew about completely demagnetizing a magnet by heating to straw color but I was unaware of how bad it was to repeatedly run them at slightly elevated temps.
They'll still gather iron filings but eventually they weaken to the point where the pan magnet field strength is eclipsed by the field strength of the electromagnet coils in the control solenoids.
As the field strength of the pan magnet decreases the loose iron filings will gather on the control solenoids.
When you add iron filings to an electromagnet the field strength increases in an uncontrolled and unpredictable manner. Similar to modifying the iron winding core of a transformer with an angle grinder. Basic High School Physics.
The TCM or PCM is programmed to vary the current flow to the solenoid coils, and thus the magnetic field of the solenoid coils, based on a solenoid that hasn't been modified (poisoned) by additional iron. When you poison the solenoids in this manner you get erratic operation because the additional iron keeps the field from pushing the iron plungers at the same rate as a fresh solenoid.
Eventually the TCM or PCM will get upset about it. Well before the controller notices and gets upset you get accelerated clutch wear, additional heat from the loosey goosey clutch engagements, and sometimes shock damage to things like the sun shell and the sprags from the erratic clutch engagement.
This all is one of the reasons I run an inline Magnefine filter in my transmission cooler return line. The magnet is properly specced for the operating temps and the additional 25 micron paper filter element doesn't hurt anything. They have a bypass function to make up for a plugged paper filter element. I can change the filter when I change my engine oil and filter. With the drain plug in the transmission pan there's no reason to drop the pan since the inline filter is 25 microns. The pickup strainer screen that filters at 100+ microns will never see enough crud to plug up.