Hey guys, new to the site. 2001 superduty 4x4 5.4. So upon fixing trans dipstick tube leak, i figured i drop pan and change filter and fluid. So drained pan, new filter in, cleaned the pan good, bolted her up and decided i wanted all new fluid in entire circuit. Dex/merc it is. Followed procedure of removing rear cooler line and adding 7 qts, pump out till bubble etc. Etc. So all was going well where as the bypass would spit a little then stop shortly after and fluid would flow from return line to bucket..it seemed to flow at a slow rate and i had no clue as to how fast it should be flowing but i kept on. 3 cycles of fill/ pump and run through gears on one of those went well until the 4th time when i started the truck i heard what sounded like clinking clanging metal for a second or two and then bypass started pouring fluid..i figured bypass was stuck open and thats what i heard possibly. So i replaced the bypass with a new one and did the check again to make sure the new bypass was closed and its still pouring out? Whats strange is the return line at the same time is pumping fluid pretty good and passes flow test now? About a qt in 12 seconds..Fluid was prolly too cold to begin with as i turn on uninsulated garage thermostat when im in there and fluid was cold so hense slow flow at first? What else can cause bypass to pour at same time as return line? New bypass faulty? Coolers arent blocked. Fluid too thick from cold?Can this happen with colder fluid? And will it correct itself if fluid warms with driving? Between the noise i heard which seemed odd and bypass still open im a little hesitant to drive. Any ideas? Sorry for the damn novel lol.

 

How do you know that?
Yes.
Yes.
Most likely. If not you will notice higher temperatures.

 

Cooler circuit is not blocked as it passed the flow test. Ok guess its normal for both to pump if colder.