BTO
Member
Nope. I'm in California.
Auto Trans operating Temps
- Thread starter SIKHILUXSURF
- Start date
quicksilvr
New member
Not necessarily concerned with that little window per se right now, but moving forward into colder temperatures I'm going to be seeing how fast the trans warms up when it's 30 degrees outside. And 0 degrees outside. And -20 degrees. Right now, I already observe a noticeable difference between how long it stays down around 110 when comparing 90 degree ambient temps to 65 degree ambient temps. When it's 65 out....it sitting down there around 110 alot longer than I guessed it would.
The 110 degree cutoff is based on several things. As a specific number, it's just what I've set my mind on. And it's still a generality. Here's how my thinking goes:
1) All lubricating fluids are engineered to have certain viscosity, and they work optimally at that point. This is based on operating temperature, since viscosity changes with temperature. ATF in general is designed to operate in the 175 ballpark range, based on automotive transmissions in general.
2) Toyota (and MANY other manufactures) design the factory transmission cooler in the radiator, so that it can warm up quicker, and remain at that elevated temperature. The ECM has a parameter where it won't even let the transmission upshift or go into lockup if the transmission fluid temperature has not warmed up enough. Granted this is fairly low.
3) Several reputable transmission specialists that I have talked to in the course of my life and my own wrenching on vehicles have refered to anything BELOW 120 degrees as too COLD. In reference to continuous operating temperature. 110 is a generous bit below that even.
4) More than anything, consistency is pretty key. Coolant and engine oil temps do this: cold -->warm up quickly and steadily -->operating temp....and they stay right there, varying very little. When it's not regulated by a in-radiator cooler, ATF does this: cold --> warm up slowly --> plateau here and there (sometimes very low) --> peak --> drop --> peak --> drop --> etc. The "operating" temp isn't really a fixed thing. And even though it's still not a fixed thing when you ARE getting the transmission warmed up quicker....it's a greater % of time spent at an optimal temp, and smaller % of time spent an un-optimal temperature.
See above.
You live in a southern climate with much smaller range of temperatures. I doubt your trans runs at less than 130-140 degrees for very long ever.
Bottom line: I'm not flipping out or anything here. I just am going to see what happens when it's 0 degrees outside and my transmission fluid has nothing to warm it up but the friction of the transmission. If it doesn't get warm enough, I'll be putting in a new radiator and running through that.
quicksilvr
New member
Cold fluid obviously still works in a transmission, otherwise we couldn't drive in the winter. The issue is operating viscosity. ATF is designed to work through a huge range of temps...but work optimally at warmer temp. It's simply not engineering to be using continually at sub-100 degree temps. Transmission will be working too hard to move the fluid around, and over time you'd probably see issues.
Your transmission isn't going to start slipping if the fluid is cold for 10 minutes. But if you way overcooled your trans, and drove for a year.....something would probably give up on the inside of the transmission.
Qyota
New member
This is incorrect. The shift point from second to third is based on the coolant temp and RPM, not the transmission fluid temp.
You have good points about viscosity, but I'd still like to see some data/analysis that supports your ideas about transmission failure due to cold fluid. About the only thing we can do is "observe and report".
So yeah, let's keep this thread going through the fall and winter. I'm in southern Wisconsin, so we'll see plenty of sub-zero temps. :snacker:
BTO
Member
Qyota
New member
I tend to agree. On very cold days, my coolant will not get hot enough to open the t-stat (which is either ~180 or ~190 degrees). Depends on the duration of the drive, and whether it is highway speed or not. In these cases, the radiator is as cold as the trans fluid anyway...so running through it would not heat it any faster than an external cooler situation.
quicksilvr
New member
I understand exactly what you are saying, I should have clarified a little more.
When my coolant temp says it's 160....the coolant in the radiator is still ambient temp. So when my coolant reads 160, and my ATF reads 90, there still is ZERO benefit to having the ATF running through the radiator....cause the radiator is not 160. However: just this morning (one of the cooler mornings to date), my coolant hit 190.....and my ATF was still 105. At that point, the radiator IS starting to warm up, and the benefit of having the ATF run through is becomes obvious if you want to warm up the ATF.
EDIT: quasi-ninja'd by Qyota....lol. Said the same thing, but differently.
hey guys,
i was driving up to my cabin in today in the snow and had 4wd going. on the way up just before getting there (20+miles of soild uphill) my ATF temp on my scangauge read 270! I am a little concerned this is too hot. I have a B+M 70268 that completely bypassed the stock cooler. Outside temps were about 10F so very cold, and even so there were really high ATF temps! Going over other passes it spiked at maybe 200, otherwise it was running from 130-180 so about what you guys are averaging.
any thoughts on this?
thanks!
i was driving up to my cabin in today in the snow and had 4wd going. on the way up just before getting there (20+miles of soild uphill) my ATF temp on my scangauge read 270! I am a little concerned this is too hot. I have a B+M 70268 that completely bypassed the stock cooler. Outside temps were about 10F so very cold, and even so there were really high ATF temps! Going over other passes it spiked at maybe 200, otherwise it was running from 130-180 so about what you guys are averaging.
any thoughts on this?
thanks!
AddictedOffroad
New member
When you see the temps spike above 220 degrees push the OD OFF button. It locks the torque converter and you will see temps drop immediately. 270 degrees is way too hot. Your tranny will not last long like that.
. all of the temps were off my scangauage.
quicksilvr
New member
More data from my observations in cold weather (below freezing):
[all temps recorded with a ScanGauge II]
-Driving around town, by the time my coolant temp hits 180, my transmission is reading 120ish. It takes about 3 full stop/go cycles for the trans to get warm. In town, not an issue at all....having the ATF running through the radiator wouldn't really be beneficial for warming.
-HOWEVER: It is a whole different story if I get right on the highway. Here is a good example of a typical winter scenerio....
Last night after Thanksgiving at the parents place, I went out and started the 4Runner to let it warm up in the driveway. I was going to be carrying a sleeping 1 year old out and putting him in his car seat....so the cabin needed to be fully warm. We get loaded up, and the coolant temp is all the way up at 190. ATF is reading 85. Pull out of the driveway, easy start down hill towards the highway for 1/4 mile. Accelerate onto the highway, ATF peaks at 120. But as soon as the torque converter locked up, ATF dropped to 97 degrees. Ambient air temp was about 25, we were going 70mph. After 17 miles of highway driving....the ATF had only crept up to 106.
Now, I'm still evaluating how I feel about this, and I'm going to try to get some more input from transmission gurus. It seems like that might be a bit too cold for constant operating. But since the TC is locked, maybe it's not hard on anything. In my mind, it kind of seems like a self-solving issue: if the transmission is moving a bunch of fluid around, it WILL warm up. If it's not, then the fluid might not get very warm...but it doesn't really matter.
What say you all? I simply want to keep my transmission safe and healthy. Which means avoiding the strawberry milkshake, AND keeping the temps good throughout a WIDE range of ambient air temps and varied driving styles. Knowing that my current cooling setup is considerably different from the one the Toyota engineers designed is what makes me even ask these questions.
[all temps recorded with a ScanGauge II]
-Driving around town, by the time my coolant temp hits 180, my transmission is reading 120ish. It takes about 3 full stop/go cycles for the trans to get warm. In town, not an issue at all....having the ATF running through the radiator wouldn't really be beneficial for warming.
-HOWEVER: It is a whole different story if I get right on the highway. Here is a good example of a typical winter scenerio....
Last night after Thanksgiving at the parents place, I went out and started the 4Runner to let it warm up in the driveway. I was going to be carrying a sleeping 1 year old out and putting him in his car seat....so the cabin needed to be fully warm. We get loaded up, and the coolant temp is all the way up at 190. ATF is reading 85. Pull out of the driveway, easy start down hill towards the highway for 1/4 mile. Accelerate onto the highway, ATF peaks at 120. But as soon as the torque converter locked up, ATF dropped to 97 degrees. Ambient air temp was about 25, we were going 70mph. After 17 miles of highway driving....the ATF had only crept up to 106.
Now, I'm still evaluating how I feel about this, and I'm going to try to get some more input from transmission gurus. It seems like that might be a bit too cold for constant operating. But since the TC is locked, maybe it's not hard on anything. In my mind, it kind of seems like a self-solving issue: if the transmission is moving a bunch of fluid around, it WILL warm up. If it's not, then the fluid might not get very warm...but it doesn't really matter.
What say you all? I simply want to keep my transmission safe and healthy. Which means avoiding the strawberry milkshake, AND keeping the temps good throughout a WIDE range of ambient air temps and varied driving styles. Knowing that my current cooling setup is considerably different from the one the Toyota engineers designed is what makes me even ask these questions.
99runnerwa
New member
At what temp does the at overtemp light come on? i was doing a long hill climb in 4 hi and it came on. i swaped out the fluid and it didnt look or smell burnt.
AddictedOffroad, when you turn off o/d it no longer lets your torque converter slip?
AddictedOffroad, when you turn off o/d it no longer lets your torque converter slip?
quicksilvr
New member
How is your ATF cooled right now? Factory cooler in radiator? Or aftermarket?
I don't know when the overtemp light kicks on....I was under the impression that is was somewhere around 300 degrees.
99runnerwa
New member
right now it is stock going through the radiator.
quicksilvr
New member
I see.
To answer your other question, when you turn O/D off, it simply keep the torque converter locked in high gear, no matter what. And it also doesn't let you drive in your over-driven top gear. It has to unlock to let you keep driving if you slow down....since you can sit in park and drive with the O/D off. If the tq converter was locked you couldn't do that.
Play with it sometime if you have a trans-temp gauge. I did the other day, and it was interesting to see my trans temp stay low on a hill climb even with the engine RPM over 3K. If I would have had O/D on, the trans would have typically gained about 10 degree F on the same hill.
AddictedOffroad
New member
Correct. It locks the torque converter when under load. You will see immediate drops in temps. FWIW, the A/T temp light comes on at 300* which is WAY TOO LATE. If that light comes on, you have already damaged the tranny in some way, shape, or form. The tranny will start to physically break down above 250*.
That OD Off light is your saving grace.
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AddictedOffroad
New member
In all honesty, I wouldn't worry about it. I just did a 350 miles trek from Windsor, CO to Penrose, CO and back. Both trips to and from were well below freezing at 75mph+ hwy speeds. I bypassed my stock cooler as well and run a large Hayden cooler. My temps ran around 125-130 degrees the whole way. They maxed around 175* on a couple hills pulls.
If the tranny were running much cooler than 75 degrees, then I would worry more, but I honestly don't see an issue with it. Even at 75 degrees its still running thin at those temps. Clutch packs are still generating plenty of heat as well.
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quicksilvr
New member
Thanks for the input Scotty. I was tending towards the same thinking. This is the first winter I've had with an aftermarket trans cooler, so I just wanted to ensure that there was no way I was over-cooling when it's really cold out.
I am going to ADD a cooler inline with my current cooler for summer time, and set it up so I can easily bypass the second cooler during the winter. The one time I towed a trailer this summer, I was getting close to 225, and I wasn't even climbing any real hills. One cooler for winter, two for summer...should work like a charm.
I am going to ADD a cooler inline with my current cooler for summer time, and set it up so I can easily bypass the second cooler during the winter. The one time I towed a trailer this summer, I was getting close to 225, and I wasn't even climbing any real hills. One cooler for winter, two for summer...should work like a charm.
99runnerwa
New member
quicksilvr, does having the o/d off while the shift lever is in 2nd have any effect? i think from now on any time i leave the pavement i will turn the o/d off.
addicted, any idea what the weak link is that would be damaged first? like i said i swapped out the fluid as soon as i got back home, and i havent noticed any issues with the transmission since, though that doesnt exactly mean nothing is wrong. oh and the fluid actually still looked and smelled new when i drained it.
addicted, any idea what the weak link is that would be damaged first? like i said i swapped out the fluid as soon as i got back home, and i havent noticed any issues with the transmission since, though that doesnt exactly mean nothing is wrong. oh and the fluid actually still looked and smelled new when i drained it.
