I've been reading a bunch of threads on external trans coolers but I haven't seen anyone mention if the trans can be too cold. My main reason for the upgrade is to separate the systems. My concern is that I live in a colder climate and running cold oil can be just as bad as running hot oil. I have an oil cooler on my car with a built in thermostat so it won't move oil to the cooler until 160. My truck is currently stock and I don't tow, so is there any risk of it running to cold? Is there a built in thermostat in the stock system or can I add one? Thanks in advance.
Trans cooler, too cold??
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quicksilvr
New member
I've been watching my temps with a SGII on my '01...and it still has the factory cooler. I haven't installed the 70264 yet. Today actually. 
Anyway....with the factory cooler, the fluid stays pretty cold. Like, barely breaks 100 degrees F when it's 5 degrees outside. Running an external cooler that has the LPD design will easily let the fluid warm up to 100 degrees.
So my answer, after watching temps with external coolers and with stock coolers....is no. It won't make it too cold.
Anyway....with the factory cooler, the fluid stays pretty cold. Like, barely breaks 100 degrees F when it's 5 degrees outside. Running an external cooler that has the LPD design will easily let the fluid warm up to 100 degrees.
So my answer, after watching temps with external coolers and with stock coolers....is no. It won't make it too cold.
the great him
Elite Member
im running dual coolers, and its not too cold, i still see temps on average of 140-160 with normal driving and i live in Vancouver Wa. some days/nights when its really cold out and when its raining it will drop down to like the 130 range, but yeah they stay warm enough to be fine imo
thanks for the responses. So I was reading about the low pressure drop system. Correct me if I'm wrong, but to make sure the fluid gets to temp, the cooler relies on the viscosity of the fluid not being able to go through the cooler when its cold? I just read that off some form so it could be wrong since I don't see where pressure comes into play.
Drcoffee
Senior Member
It will either be too cold or too hot with just the external cooler. The radiator helps modulate the transmission temp. When you start your truck, the coolant warms the transmission faster and when you are running hard the coolant cools the transmission. Under extreme use, an external cooler will help keep the temps inline. I know the risk of a factory radiator failure is high, so just buy a new radiator and replace it.
Flame suit is now in place: :flamethrwoer2: :moon:
Flame suit is now in place: :flamethrwoer2: :moon:
quicksilvr
New member
Lol, flame suit.
After seeing real life temps of both setups....I have to disagree. The radiator does literally nothing to warm the fluid on cold days. Unless of course you let your truck sit and idle for like 30mins on every cold start. Hopefully no on is doing that.
Factory cooler: Cold start, idle for 10 mins - result is 150 water temp and the thermostat hasn't opened yet, so the radiator is still totally cold. ATF still only 60-70 degrees after 10 mins.
External cooler: Cold start, idle for 10 mins - result is 150 water temp and ATF is again, about 60-70. The ATF warms up when you drive. No two ways about it.
Factory cooler keeps temps around 150 during the winter. External cooler keeps temps around 150 during winter. I haven't compared summer data, because I don't have it. But I bet they're close again, with the external cooler actually keeping it cooler than the factory. If you use an adequate sized cooler.
Bottom line, at least for me anyway: A radiator is only slightly more expensive than a cooler. And it no harder to change than it is to install a cooler. Basically, there are no reasons keeping me from doing one or the other, other than which I feel is more effective. I bypass the radiator, and use a cooler every time.
Oh, and I've installed 5 cooler's on 4 different 4runners at this point. :bigok:
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I don't know about the rad keeping the trans warmer. If its that cold that your trans needs warming from the rad I would think the engine would be just as cold without the thermo being open. I do agree though that it would modulate the temperature better keeping the trans engine and rad all about the same. I have no data though, 150 F seems kind of cold though for trans temp. oil thermostats usually dont open until 160. I think if I do go for a cooler a gauge is in order. What is normal operating temperature for these autos? 180ish?
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PitbullRescuer
New member
I have to agree with Quicksilvr. I posted this a few times today, an external cooler is absolutely worth the few extra $'s just to guarantee you'll never have the milkshake. I installed mine in January and the trans has been fine. No issues shifting, taking longer to warm up, etc. Works just like it did when it was runnig through the radiator.
quicksilvr
New member
No, absolutely not. 150 is great for ATF. I think in a perfect world ATF would always be 165-170. No lower and no higher. In our imperfect world, modulating it between 120 and 180 is about as good as it gets.
Don't ever use one of those. It'll make your trans run hotter than it should more often than it should. Every person I know that's used one has taken it off and wished they never got it.
Here's my story, I have the b&m cooler, the small one
This morning it was showing -5f on the outside temp gauge in the dash, I let her warm up for 15 minutes and the scan gauge tranny temp said 70f. With in a couple blocks it went up to 100f and climbed to 120f. I hit the highway at 60mph, air intake temp showed -5f and temp gauge in the dash was -9f. Tranny temp pretty much hovered around 110f for a 15 minute drive.
The tranny shifts fine and I don't pound it till its warms up, though 110 ain't very warm at all imo.
I did a trip to the mountains a couple weeks ago, and motoring along the highway at 70mph it ran around 130 ish but it was around 20 or so. Then there was like 5 miles of pretty steep road to get to the ski hill, lotsa 35-40 mph, and the tranny temp did get as high as 193f.
So it does seem too cold below 0 and if I was pulling a trailer up a steep hill I bet it'd be well over 200f maybe.
shayne
This morning it was showing -5f on the outside temp gauge in the dash, I let her warm up for 15 minutes and the scan gauge tranny temp said 70f. With in a couple blocks it went up to 100f and climbed to 120f. I hit the highway at 60mph, air intake temp showed -5f and temp gauge in the dash was -9f. Tranny temp pretty much hovered around 110f for a 15 minute drive.
The tranny shifts fine and I don't pound it till its warms up, though 110 ain't very warm at all imo.
I did a trip to the mountains a couple weeks ago, and motoring along the highway at 70mph it ran around 130 ish but it was around 20 or so. Then there was like 5 miles of pretty steep road to get to the ski hill, lotsa 35-40 mph, and the tranny temp did get as high as 193f.
So it does seem too cold below 0 and if I was pulling a trailer up a steep hill I bet it'd be well over 200f maybe.
shayne
quicksilvr
New member
^^This is identical to what a stock cooler would do.
And pulling up a long grade will always warm the tranny up good. The 70264 is the one that is big enough to keep it under 200 pretty much no matter what. The 70268 won't. I know I saw 220 when climbing Slumgullian Pass in CO....with the 70268 installed.
And pulling up a long grade will always warm the tranny up good. The 70264 is the one that is big enough to keep it under 200 pretty much no matter what. The 70268 won't. I know I saw 220 when climbing Slumgullian Pass in CO....with the 70268 installed.
A.Wilson013
New member
I have the 70268. I drive up and down mountains almost every weekend to snowboard in the winter, or MTB in the summer. The ONLY time I have EVER seen my trans temp gauge over 200 was when I was nearly stuck in very loose, very deep, sand and a rather warm PNW day. (I think it was ~80 in Pacific City) I was in 4 Lo, spinning all 4 tires, and moving about a foot every couple of seconds for about 30 seconds.
On the other side of the spectrum- if it's cold and raining, I will not get over 75 degrees on the freeway. That's with the cruise at 60mph like it is 99% of the time.
Typical everyday driving I am consistently between 105-135 mixed highway/suburb roads.
On the other side of the spectrum- if it's cold and raining, I will not get over 75 degrees on the freeway. That's with the cruise at 60mph like it is 99% of the time.
Typical everyday driving I am consistently between 105-135 mixed highway/suburb roads.
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Martinjmpr
New member
Well, I don't have a trans temp gauge yet (will be ordering a Scangauge II soon) but even with the very cold temps we've had in CO since December I have had zero "issues" with my B&M tranny cooler.
I do park in a garage and I almost always let the engine warm up for a couple of minutes before driving. But heck, I do that with all my vehicles including my DD which has a manual tranny. :shrug:
I do park in a garage and I almost always let the engine warm up for a couple of minutes before driving. But heck, I do that with all my vehicles including my DD which has a manual tranny. :shrug:
phailing101
New member
Resurrection!
I was just chatting with my mechanic and he's trying to talk me out of installing my Hayden 1678 to completely bypass the radiator. He's worried the transmission will not warm up in the winters enough and will therefore be at risk.
I live in Saskatchewan (Canada) where winters are normally 2-3 months of -22F (-30C).
It sounds like some folks think this shouldn't be an issue but does anyone live in a cold climate that have real world experience? Or professional opinions for that matter?
I was just chatting with my mechanic and he's trying to talk me out of installing my Hayden 1678 to completely bypass the radiator. He's worried the transmission will not warm up in the winters enough and will therefore be at risk.
I live in Saskatchewan (Canada) where winters are normally 2-3 months of -22F (-30C).
It sounds like some folks think this shouldn't be an issue but does anyone live in a cold climate that have real world experience? Or professional opinions for that matter?
quicksilvr
New member
I'll throw my .02 on this. I think your best course of action is going to depend heavily on exactly how you drive. When you do your driving in those really cold temps, do you start the truck, and then get driving on a highway pretty quickly? Or do you drive around town a lot at first?
For example, some people pull out of their driveway, drive 1/2 mile on a gravel road, and then hit the highway for 30 miles. In this situation, your transmission is going to run REALLY cold in those temps. I doubt it would break 80 degrees F. But if you do a lot of starting, stopping, accelerating right off the bat, the trans WILL warm up to a good temp and be fine.
the great him
Elite Member
in your case i would probably still get one, but maybe put a "Y" with a selectable diverter valve in the line so you can run the aftermarket trans cooler in the summer, and then stock set up in the winter, i would also recommend getting a new radiator as well. i would advise getting a trans temp gauge so you can see what its doing and where your temps are at, this way you can pic and choose how and when to run your temps. just my thoughts, and what id do if it was me.
