Transmission Overheating - anyone else?

[jarussell4]

UPDATE
So, the case manager called me today and after further review by Toyota and their Field Tech, they concluded that these are not abnormal temperatures and that there is nothing wrong with the vehicle that it is running as it should, so the case will be close with no further investigation needed. Wow!!!! So I am stuck with a Furnace!!! Lets hope the tranny lasts. I am VERY dissapointed at Toyota so far. Is almost like instead of keeping the high standards of the past, they said, well let's just lower them, since all the other manufacturers are doing it, then we will too.
For those of you that know these Toyotas better than me. Should I still take it to Toyota for the Fluid to be flushed and replaced? If I pay out of pocket, how much should I expect for a tranny flush on this vehicle?

 

[TakaraLC]

I think alert level is set to something like 300F, where fluid starts to break down.

 

[Bad1975]

I doubt Toyota will flush, drain and fill sure. I didn’t see any flush procedure in TIS.

Flushing is fairly difficult on any modern transmission with all the check valves temp and/or pressure sensitive, and cooler and such.

Easiest DIY to get near a flush would be 3 drain and fills with driving between to get the fluid cycled through every where.

May be possible to tap into one side the cooler and flush to pan with the temp solenoid pinned? Not sure if pinning it locks it open or closed though. This also won’t flush anything in the TC, valve body or behind check valves. This would have to be done with very low pressure 2-3 psi max as nobody knows what and where the fluid is moving through in the system.

Safer to just do multiple drain and fills, take total fluid capacity and drain and fill with driving between until you replaced at a minimum the total capacity on your drain events then do one final drain and fill.

Ideally for a proper flush the over flow would be left open with the vehicle up and running in gear on a lift with a fill hose running probably at the cooler and fluid that is pumped in is preheated. Dangerous endeavor as too much or too little fluid can cause damage and if any air pockets occurred it could also cause problems it has to remain in the proper temp range to maintain the proper level during this process. That why I don’t think Toyota or any other manufacturer would do a flush in the modern age.

Will be interested to know if OTT tune corrects or reduces this issue. My experience shows it’s all related to Tc lock-up and lack there of due to shift logic programming. I wonder if ECO, Normal and Sport and/or Tow haul would have some smaller affect to limit the rise in the scenarios it occurs in?

In the mean time I’ll just switch to manual shift when the gauge rises or go to 4LO if situation warrants and permits. Anything sustained at 250F (IIRC this is when the warning goes off) and above degrades fluid life. Not sure if the warning is triggered by sensor 1 (Pan) or sensor 2 (TC). Also not sure if fluid goes from pan>tc>cooler>pan or something else?

 

[ultane]

I doubt Toyota will flush, drain and fill sure. I didn’t see any flush procedure in TIS.

Flushing is fairly difficult on any modern transmission with all the check valves temp and/or pressure sensitive, and cooler and such.

Easiest DIY to get near a flush would be 3 drain and fills with driving between to get the fluid cycled through every where.

May be possible to tap into one side the cooler and flush to pan with the temp solenoid pinned? Not sure if pinning it locks it open or closed though. This also won’t flush anything in the TC, valve body or behind check valves. This would have to be done with very low pressure 2-3 psi max as nobody knows what and where the fluid is moving through in the system.

Safer to just do multiple drain and fills, take total fluid capacity and drain and fill with driving between until you replaced at a minimum the total capacity on your drain events then do one final drain and fill.

Ideally for a proper flush the over flow would be left open with the vehicle up and running in gear on a lift with a fill hose running probably at the cooler and fluid that is pumped in is preheated. Dangerous endeavor as too much or too little fluid can cause damage and if any air pockets occurred it could also cause problems it has to remain in the proper temp range to maintain the proper level during this process. That why I don’t think Toyota or any other manufacturer would do a flush in the modern age.

Will be interested to know if OTT tune corrects or reduces this issue. My experience shows it’s all related to Tc lock-up and lack there of due to shift logic programming. I wonder if ECO, Normal and Sport and/or Tow haul would have some smaller affect to limit the rise in the scenarios it occurs in?

In the mean time I’ll just switch to manual shift when the gauge rises or go to 4LO if situation warrants and permits. Anything sustained at 250F (IIRC this is when the warning goes off) and above degrades fluid life. Not sure if the warning is triggered by sensor 1 (Pan) or sensor 2 (TC). Also not sure if fluid goes from pan>tc>cooler>pan or something else?

Thank you!

 

[Bad1975]

Thank you!

No thanks needed, just passing info and observations.

The multiple drain and fill method is what I do for the Tundra at 100k interval and our Volvo at the same along with filter change, don’t think the 250 series filter is available readily anywhere other than Toyota.

Fluid was still good on both but beginning to stray to brown vs red.

I also use this across multiple vehicles which makes maintenance much easier and cleaner. Works all the way up to 85-95w fluids quite well. Mine is the original maker but same deal as this and even use it at work occasionally:

https://a.co/d/eBRg3CA

 

[RUN-8]

UPDATE
So, the case manager called me today and after further review by Toyota and their Field Tech, they concluded that these are not abnormal temperatures and that there is nothing wrong with the vehicle that it is running as it should, so the case will be close with no further investigation needed. Wow!!!! So I am stuck with a Furnace!!! Lets hope the tranny lasts. I am VERY dissapointed at Toyota so far. Is almost like instead of keeping the high standards of the past, they said, well let's just lower them, since all the other manufacturers are doing it, then we will too.
For those of you that know these Toyotas better than me. Should I still take it to Toyota for the Fluid to be flushed and replaced? If I pay out of pocket, how much should I expect for a tranny flush on this vehicle?

If you’re this concerned about the transmission fluid temps, and you steadfastly refuse to use low range in your transfer case you have two choices for your own sanity:

1.) Have the transmission fully flushed, and have a dedicated air to liquid radiator style cooler installed for transmission fluid.

2.) Sell it and get something else.

 

[TakaraLC]

If you’re this concerned about the transmission fluid temps, and you steadfastly refuse to use low range in your transfer case you have two choices for your own sanity:

1.) Have the transmission fully flushed, and have a dedicated air to liquid radiator style cooler installed for transmission fluid.

2.) Sell it and get something else.

I think EOD Guy mentioned that his dealer warned him about installing an aux trans cooler would void the drivetrain warrant. So that is also something to consider.

 

[KyLandcruiser]

Installing an extra transmission cooler can not void the warranty. The warranty can only be denied if the extra transmission cooler caused the failure.

 

[RUN-8]

I think EOD Guy mentioned that his dealer warned him about installing an aux trans cooler would void the drivetrain warrant. So that is also something to consider.

Some dealers do tend to delight in threatening to void warranties.

Under the Magnuson Moss Warranty act they would have to prove that a modification caused a failure in order to void a warranty. The cost of the legal fight should be considered though even if you “win”.

People freaking about about fluid temperature changes, and oil pressure variations is one of many reasons those data points are hidden from end users to be replaced with idiot lights and error messages.

95% of end users will never pay attention to the gauges regardless of how accurate they might be (hence the idiot light or error messages), 2% will know what they are and learn what normal ranges are for whatever is being monitored/measured by the gauge.

The last 3% will know what the gauge measures, but will not accept the “normal” range of temps or pressures insisting that their preferred range of acceptable figures has to be right. They will determine the system is operating abnormally and waste countless man hours of service writers, technicians, and field service engineers verifying that everything is in fact normal.

 

[KyLandcruiser]

Something I’m curious about is in either 1st or 2nd gear I believe it’s 1st right before a shift at 3K RPMs the torque converter seems to lock up. The RPMs drop a few hundred before a shift. This doesn’t always happen. This just seems kinda odd but probably normal.

 

[EOD Guy]

The addition of a cooler in it's self would not void the warranty, however I could see where it would be very easy for a dealer to establish that the installation, restricted flow, introduced debris into a sealed system, loss of fluid due to a punctured core etc.............which contributed to the transmission failure.

What I was looking for was a dealer installed solution for a transmission cooler that would maintain the warranty if any of the above happened. Which the dealer said "nope".

 

[jarussell4]

If you’re this concerned about the transmission fluid temps, and you steadfastly refuse to use low range in your transfer case you have two choices for your own sanity:

1.) Have the transmission fully flushed, and have a dedicated air to liquid radiator style cooler installed for transmission fluid.

2.) Sell it and get something else.

I just want to point out that this is not an isolated issue—it’s something other owners have also experienced, not just me.


I’m not criticizing anyone or any brand, so please don’t take my comments personally.


I’ve mentioned before that it’s not only on trails where I might need 4LO. Sometimes it’s on winding highways where speeds are 20–45 mph, and in those situations, other vehicles I’ve driven (for example, my wife’s Prius) keep transmission temps well under 200°F. In these cases, using 4LO would not be practical or safe.


This situation reminds me of the earlier braking noise concern that led to a TSB. Even though I didn’t have that problem myself, I still supported those who did, because their experience was valid.


I’m sharing this so we can compare notes and help each other—not to attack, criticize, or tell anyone what to do. My only goal is to contribute to the discussion about an issue others have also seen with this engine/transmission combination (including in Tacomas and 4Runners).

 

[jarussell4]

Some dealers do tend to delight in threatening to void warranties.

Under the Magnuson Moss Warranty act they would have to prove that a modification caused a failure in order to void a warranty. The cost of the legal fight should be considered though even if you “win”.

People freaking about about fluid temperature changes, and oil pressure variations is one of many reasons those data points are hidden from end users to be replaced with idiot lights and error messages.

95% of end users will never pay attention to the gauges regardless of how accurate they might be (hence the idiot light or error messages), 2% will know what they are and learn what normal ranges are for whatever is being monitored/measured by the gauge.

The last 3% will know what the gauge measures, but will not accept the “normal” range of temps or pressures insisting that their preferred range of acceptable figures has to be right. They will determine the system is operating abnormally and waste countless man hours of service writers, technicians, and field service engineers verifying that everything is in fact normal.

I’m sharing actual data from a scan tool—not relying on the “idiot gauge” in the dash. These are direct temperature readings from the transmission, not estimates.


For reference, Toyota ATF WS is a low-viscosity synthetic fluid designed to meet JWS 3324 specs. Industry data and Toyota’s own service literature show that:

• Ideal operating range: ~175–185°F (80–85°C)
• Accelerated oxidation: starts above ~220°F (104°C)
• Severe degradation: above ~250°F (121°C), fluid life drops drastically
• At ~275°F (135°C): fluid life can be reduced to less than 10% of normal, risking varnish, seal hardening, and clutch material breakdown

If ATF WS consistently runs hotter than these ranges, it will degrade far earlier than Toyota’s “lifetime” expectation. Once degraded, the fluid loses its ability to lubricate and cool, which can lead to premature wear and, eventually, early transmission failure. This lines up with reports from some owners who’ve experienced transmission problems well before expected service life.


The reason some owners don’t see high temps under similar conditions is likely due to differences in driving style, terrain, load, ambient temperature, and even individual manufacturing tolerances. Others—like me—do see elevated temps, and it’s worth documenting because fluid chemistry doesn’t care about brand loyalty; the breakdown thresholds are the same for everyone.


This is not opinion—it’s consistent with measured data and the known performance limits of Toyota ATF WS.

 

[RUN-8]

I’m sharing actual data from a scan tool—not relying on the “idiot gauge” in the dash. These are direct temperature readings from the transmission, not estimates.


For reference, Toyota ATF WS is a low-viscosity synthetic fluid designed to meet JWS 3324 specs. Industry data and Toyota’s own service literature show that:

• Ideal operating range: ~175–185°F (80–85°C)
• Accelerated oxidation: starts above ~220°F (104°C)
• Severe degradation: above ~250°F (121°C), fluid life drops drastically
• At ~275°F (135°C): fluid life can be reduced to less than 10% of normal, risking varnish, seal hardening, and clutch material breakdown

If ATF WS consistently runs hotter than these ranges, it will degrade far earlier than Toyota’s “lifetime” expectation. Once degraded, the fluid loses its ability to lubricate and cool, which can lead to premature wear and, eventually, early transmission failure. This lines up with reports from some owners who’ve experienced transmission problems well before expected service life.


The reason some owners don’t see high temps under similar conditions is likely due to differences in driving style, terrain, load, ambient temperature, and even individual manufacturing tolerances. Others—like me—do see elevated temps, and it’s worth documenting because fluid chemistry doesn’t care about brand loyalty; the breakdown thresholds are the same for everyone.


This is not opinion—it’s consistent with measured data and the known performance limits of Toyota ATF WS.

Time to sell your LC then.

Or have a transmission cooler installed.

Pick one.

 

[EOD Guy]

While looking through the hundreds of PDFs I have concerning the LC, I ran across the attached PDF. It appears the LC has a water/coolant to oil transmission cooler. It appears to be rather small and I'm not sure if it's just for the Inverter or the actual transmission.