I've done several tranny fluid changes, and fluid cooler line disconnects to drain out the old fluid from the cooler. I let it drain for serveral hours, I never get in a hurry.
I can get 10 qt out, my question is how can I flush the TC? Or does new fluid get pump in every so ofton? Do I need to worry about it.? I run it hard pulling heavy loads, for example out of the hole, I'm full into the pedel up to overdrive, the truck and trailer weights 11,600.
Most of the time total weight is over 23K.

Thanks.

 

If you want a complete flush see this post:

https://www.dieseltruckresource.com/...threadid=72749

Using the engine to "pump" the fluid till it is nice bright pink (new looking), will get the fluid out of the TC.