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At what temps does the fluid bypass the cooler?

1203 Views 6 Replies 3 Participants Last post by  Griz
I am getting ready to change the transmission fluid. I plan to use Mark K's procedure. I want to change the internal filter and inspection the magnetic and clean the pan etc. since the truck is new to me. But I was wondering if I follow Mark's procedure and disconnect the return line, run the truck to pump out the fluid etc and stop after the first cycle to drop the pan, change the filter and clean the pan/magnetic...will the fluid still in the transmission cool so much it will bypass the cooler and return line I have disconnected? At what temps does the fluid stops bypassing the cooler?

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Really, the fluid should never bypass the cooler. There is a pressure valve between the two lines that allows fluid to bypass the cooler if the cooler pathway becomes obstructed. I think some people see the reverse flow when cold just because of the fluid viscosity when cold. I would suggest getting the fluid above 100° would be sufficient for the fluid change.
I never had a problem - and you're right, the fluid cools down pretty quickly. There is no temperature bypass on the tranny, so its a pretty moot point.
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