Hi there,

I was wondering how cool is too cool for this transmission to operate? What can happen from keeping it too cool? I had a tube and fin aux cooler rated for 23,000GVW routed after the radiator but off road it still got way to hot for my liking so I upgraded to a plate and fin rated for 30,000 GVW and bypassed the radiator. This seemed to lower the engine temp a few degrees as well. I have a trans temp gauge with the sender screwed into the hot line coming from the torque converter so I can see what the max temp my oil gets heated too. I know this is not the actual temp inside the trans before the converter though, that temp will be cooler.

So after driving it for a couple hours I see that the temp hangs between 160* and 180* with the temp outside at 76*. When it was 100+* the trans temp would get to 195* maybe 205* off road but no more than 210*.

Am I keeping my 46RE too cool? I have read that these transmissions like to stay around 200*. I use ATF-4 as well. I haven't tested it out on temps below 60* yet. It has no trouble shifting and goes into O.D. every time so far.
I really like the set up with the radiator bypassed but I will be moving to the D.C. area soon and I know that it's going to be much cooler than here in Las Vegas. Thanks for the input!

 

 

the only time it would be too cool is if the OD locks out. i think? not sure that's below about 160* or so.

if that happens you can get a thermal bypass to plumb into the cooler inlet.

i also recently put a big *** cooler on mine and bypassed the radiator. i think i've got a bad radiator that was no longer keeping up the combined load of engine and trans, and the engine temp was going up. bypassing the radiator has sort of band-aided it for the time being.

 

I have a Hayden upgraded trans cooler and no check valve and a temp trans gauge. Climbing big hills with over drive off, she will reach around 225-240. Never seems to get any higher than that. Flat driving and I can keep it under 180 easy.

Anything over 240 is asking for trouble... Is there such thing as too cool for those things, being that they are known to over heat?

 

I think that's a pretty old chart because ATF-4 can withstand temps up to 300* and maintain it's integrity. I would still change it anyways though. Temps of 250* sustained with ATF-4 are fine. I'm talking about fluid temp coming from the torque converter not internal transmission temp. But I am still wondering if anyone here has run into trouble with the radiator bypassed and having a large trans cooler with it running too cool? I don't even know what the effects of too cool would be. Isn't ATF-4 rated for 20* or something? I know it has superior hot and cold viscosity but I am not sure what the cold rating for it is.

I know my transmission heats to operating temp before my motor temp would help to heat it since it goes right into O.D. so far. I guess I will just see what happens with the colder weather.

I found this on the Oil Guys site http://www.bobistheoilguy.com/forums...1705531&page=2

 

The fluid(atf+4) might be able to withstand 300 degrees, but I don't think the rest of the components in the tranny will.

 

That's for sure true. I wasn't talking about the inside of the tranny being that hot. The oil can get way hotter than the trans internals coming out of the TC. Then it get cooled off but it doesn't matter how cool the oil gets after it overheats. It's toasted after that and protect the tranny after that. Pretty sure if the trans internals got that hot it would be game over.

 

I'm certain of that. At 300 degrees, you're left with polished clutches and internal leaks.

Unless it's bone chilling cold outside, allowing the outlet temperature to hit 300F for more than about half a minute is going to leave you with more heat than the internals can stand. The pump is going to move a quart or more per minute, so you can't afford to run that hot at the outlet for very long at all.

"The issue's not whether you're paranoid... the issue is whether you're paranoid enough."

 

Only way the "outside" tranny temp is going to be 300 is if the inside is hotter than that, no matter how cold it is outside the tranny will be or is toast in a matter of seconds.

 

I'll post back after a while and let you all know how it does in the Maryland/Virginia this winter. We'll be moving in a couple days and I am having the truck shipped.