Transmission running too cold?

[dwtaylorpdx]

FWIW,, ATF is usually viscosity stable in a pretty wide range,,

In a tow vehicle they usually recommend keeping the auto under
220. few auto lubricants like to be any hotter.

I believe the redline website used to have a table for proper temps,,

Redline ATF, with no cooler lowers my transfercase temp about 40 degrees on my jeep when in low range working it hard.

I think its as important to keep the temp consistent as it is to keep it low.
Thermal changes work the parts harder..

[EcoCivic]

I installed a temp gauge about a month ago and the transmission frequently doesn't even reach 100 degrees in cooler weather. I was cruising down the highway with the converter locked in about 30 degree weather and the trans temp was running a 75-80 degrees F. Is this bad for the trans? And if not, how bad is it for fuel efficiency? Thanks

[IsaacCarlson]

75-80 should be fine. I don't have a temp gauge but I do have a BIG cooler on the rav4 and they are definitely down. A bit less mileage this year with the cooler, but it shifts better and since I plow with it, that's ok.

[EcoCivic]

Originally Posted by IsaacCarlson

75-80 should be fine. I don't have a temp gauge but I do have a BIG cooler on the rav4 and they are definitely down. A bit less mileage this year with the cooler, but it shifts better and since I plow with it, that's ok.

Thanks. My trans seems to shift about the same regardless of temp, it shifts hard either way with the solenoid mods I did. Just curious how much worse your mileage is? I can't imagine that I'm losing more than 1 MPG from running the trans a bit cold, but I could be wrong. Thanks

[IsaacCarlson]

About 1 mpg is what I figure.

[Tahoe_Hybrid]

Originally Posted by hayden55

I would say yes just because you want the oil to thin out to spec. If its too cool, it is just causing extra friction and a slight loss in mpg.
I assume this car is an automatic?

MPG loss at the expensive of a LONGER life transmission


gas is cheap you would only lose like 1% while extending the life of the transmission for many many extra miles

mine runs between 145F-165F winter/summer those are the ideal temps if you want the transmission to last 300,000-400,000 miles


once you get into the 190-210F range it will last about 115-150k miles

[hayden55]

Originally Posted by Tahoe_Hybrid

MPG loss at the expensive of a LONGER life transmission


gas is cheap you would only lose like 1% while extending the life of the transmission for many many extra miles

mine runs between 145F-165F winter/summer those are the ideal temps if you want the transmission to last 300,000-400,000 miles


once you get into the 190-210F range it will last about 115-150k miles

Big maybe. Bearing gaps actually desire a specific weight. Not higher or lower.

[ksa8907]

Originally Posted by Tahoe_Hybrid

MPG loss at the expensive of a LONGER life transmission


gas is cheap you would only lose like 1% while extending the life of the transmission for many many extra miles

mine runs between 145F-165F winter/summer those are the ideal temps if you want the transmission to last 300,000-400,000 miles


once you get into the 190-210F range it will last about 115-150k miles

I would say that's an unfair relation, your transmission has no torque converter which is where the vast majority of transmission heat is generated.

[EcoCivic]

Originally Posted by hayden55

Big maybe. Bearing gaps actually desire a specific weight. Not higher or lower.

I'm not so sure about that. Most transmissions (including mine) don't come with a thermostat to keep it at a specific temperature, it actually varies a lot depending on outside temp. I know most people say that the cooler in the radiator regulates the temp and warms the fluid up, but that's not true. The cooler is in the cold side of the radiator, which doesn't even start to warm up until the thermostat opens, and can actually stay pretty cold on cool days when the thermostat isn't open much.
Some newer transmissions actually run the fluid through the hot side of the cooling system to help warm it up.

So I am pretty much thinking if the engineers weren't worried about the transmission failing from running cold I shouldn't be either, but if you have different thoughts on this please let me know.

[Tahoe_Hybrid]

Originally Posted by ksa8907

I would say that's an unfair relation, your transmission has no torque converter which is where the vast majority of transmission heat is generated.

the most stress is on the front Sun gear and input/out shaft there is a risk every time it 'starts' the it will blow apart


someone seized an engine and ended up blowing apart the transmission along with it.. i asked them why they did not have it towed , they did not say anything


it does have two 60kw electrical motors that need to be cooled to make up for it


it also comes with the heavy duty tow package ( for the cooling only since the max is 6200 pounds for 2wd )