Don't ask me, I would have to watch the video again of the guy doing the flush. I guess a case of a subject matter that was discussed so thoroughly we missed the obvious. I think Oh Six has a handle on it, if anybody does.
Frankly, I'm not sure about much. It's entirely possible I've totally misinterpreted the diagram on page 14-241 of the 06 thru 08 FSM P/NO 61SJC02. It appeared to me the fluid leaves the OTW exchanger (described as "cooler") and enters the trans.
Forum member bobcat has experience exactly opposite. So I'm unsure. There's an OSC radiator awaiting installation, when I get around to stuffing it in, more will be revealed.
See how you guys interpret the info. Below is the entire page 14-241 followed by a close up snip (boxed in red) of the text and images referring to the "cooler outlet".
EDIT:
The FSM is open to interpretation because "ATF cooler outlet hose" could mean:
A) Outlet from trans to cooler
OR
B) Outlet from cooler to trans
I read it to be B
As a heat management component, the OTW exchanger could be:
A) "pre-cooling" trans fluid before passing to the OTA cooler
OR
B) Bringing trans fluid to a predictable before entering trans
In the case of A:
Because engine temperature is "range constrained" remaining relatively stable around 180f, fluid exiting the trans is likely to be higher than engine coolant temp during normal operation/loads and for most of the vehicles life. As a pre-cooler, the OTW exchanger would be lowering temps before passing to the OTA exchanger - thereby maximizing its (the OTA) ability to drops temps even further before re-entering the trans. In this flow, old school wisdom "cooler is better" fluid temps remain in tact if for no other reason than an OTA exchanger is subject unknown ambient air temps and air flow rates - which is an engineering unknown - but would be "averaged" for predictive service life modeling.
In the case of B:
Fluid hotter than engine coolant enters the OTA exchanger dropping to whatever level it can - based on ambient temps and available air flow - before passing into the OTW exchanger. In this flow direction, the concept of the OTW serving as a "pre-heater" is supported because it is assumed engine coolant heats faster than trans fluid. Aside from that concept and assumption, it would also be a temp "stabilizer" - sending fluid into the trans at a (more or less) predictable temp (engine coolant being "range constrained" operating at a known level) supporting predictive modeling for long term service modeling, if for no other reason than "avg" trans fluid temps below 200f is generically desirable.
Either flow direction seems reasonable from a heat management perspective. Both having variables in heat transfer characteristics of ambient air temps the oil-to-air cooler is operating in, air flow rate and the temp exchange capacity of the the oil-to-water device buried in engine coolant.
In both flow directions, FSM terminology "cooler" is used when referencing both OTW & OTA heat exchangers implying under all circumstances - and in either flow direction - fluid reentering the trans is cooler than when it left (once the vehicle is "at temp").
Ambiguity, much?