Btw -- noticed recently that proper auto tranny operating temps are in the maintenance section of the manual (had looked previously in the A/T section and only found the 158*F lock up solenoid disengagement temp mentioned):
http://personal.utulsa.edu/~nathan-b...nce/2maint.pdf

Again, this suggests value in a minimum temperature range. Still torn about running a thermal bypass valve: http://www.ebay.com/itm/TRANSMISSION...-/321082407626

Where I'm at now is probably here:
I think the best option from a flow perspective (a lot of folks have said bypass valves cause overheat when towing) is to run the factory cooler/radiator in parallel w/ external cooler and replace radiator every 150k and only run toyota coolant w/ distilled water.

From tranny to cooler to radiator back to tranny is the Toyota towing package and best from the consistent tranny temp perspective as well as consistent coolant temp (tranny fluid exchanges heat w/ coolant in bottom 1/4 or so of the radiator meaning an overheating tranny adds add'l and not wanted heat to the coolant immediately before it cycles back to the block).

From tranny to radiator to cooler to back to tranny is what a lot of tranny shops recommend and causes the lowest tranny fluid temps but also risks adding extra heat to the coolant...

Either would work, but with the 3vze's heat problems, I lean towards the first right now, but am still thinking through how I want to configure (as illustrated, I have the factory towing package so have a basic but far from ideal version of the first setup currently).

And if running synthetic coolant a slight overheat of tranny fluid is less of a concern, and remember the coolant enters the radiator ~180 to 200* F and is cooled below that by the time it exits and where tranny fluid is cooled. If tranny fluid is below coolant temps, heat will transfer to tranny coolant, but from a systems perspective that isn't necessarily a bad thing... Will ensure that both are in the lower end of ideal tranny/coolant operating temps per FSM I think.

 

Sounds like this is a pretty common problem. So the general consensus is to put a quality aftermarket cooler in and bypass the OE setup?

I'm absolutely 100% going to put a brand new radiator in it... it's just something I do with all of them. As for the rupture in the radiator itself... if it ruptures on a 5sp setup (w/o trans cooler) you could/would lose your coolant if the trans cooler inlet and outlet are not capped or connected? I think i'm going to put a hose on my 5sp radiator connecting the two just in case but I have a new radiator in it.

I'll probably be installing an external cooler and bypassing the OE setup so this thread will be a huge help. The paralell idea sounds good too and if i'm putting a new radiator in it will it be safe for 150k miles? Probably won't be towing anything big enough to matter but it will be subjected to 100+ degree temps during the summer

 

Different radiators for five speeds -- no bottom tranny port thing if buying OEM. Some aftermarkets may just make one for both applications. But technically, they're separate.

Bypass if you want to be 100% sure that no red slush happens.

But, that creates problems w/ needing to ensure your AT tranny fluids is at proper temp. There is such thing as too cool, and some ATF lifetime schedule changes actually show a decreased lifespan for fluid run too cold... That is, there's a reason, your tranny won't go into OD until the engine temp reaches 158*F -- w/ factory oil to water cooler, it ensures your tranny temp is in operational range as well and that it has a viscosity that will allow fluid to properly lubricated and cool the tranny during O/D...

A lot of cost/benefit questions here. Most red slushes seemed to occur after the 120k major maintenance time period, and while the radiator replacement wasn't recommended, it seems that red slush should be able to be avoided >95% of the time if changing radiator in regular intervals...

I'm still torn on what the perfect setup is, and I've been thinking about it for a few months now... I do think that the keep tranny fluid as cold as possible all the time is the wrong route.