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I have the OEM cooler installed and I still hit temps in the 260s after my truck was working hard in some soft sand recently
Also a note that Toyota transmissions are very sensitive to fluid levels being CORRECT. After a radiator replacement on my 07 GX w/ 180k miles I was still seeing some fairly high trans temps, but when I added a bit of fluid (1/4 qt) and did the level check the temps came back down to normal levels. So it might be a good time to ensure your fluid levels are correct.
Also a note that Toyota transmissions are very sensitive to fluid levels being CORRECT. After a radiator replacement on my 07 GX w/ 180k miles I was still seeing some fairly high trans temps, but when I added a bit of fluid (1/4 qt) and did the level check the temps came back down to normal levels. So it might be a good time to ensure your fluid levels are correct.
Good idea. Was planning on a drain/fill so will makes sure the levels are correct.
I keep the AT thermostat on mine pinned open year round and have so for many years now
If I could here that is exactly what I would do as well. But by first week of Oct. and mid Oct. at the latest which is in the middle of my main towing season it will be like this here
Why I went with the bypass Hayden cooler, well and you have also mentioned that you wondered if you shouldn't have gone with a larger cooler than OEM.
The factory OEM stat at 200° is way too high IMO and pretty sure CAFE standards have everything to do with that. Hopefully the Hayden stat will fully open at a much lower temperature.
Once bird season is over I will unpin the factory bypass but pin it in the summer. I'm just hoping that I don't have to block the transmission cooler in the winter. Too cold is not a good thing either we didn't even unlock the throttles to the main engines until the oil got up to 120° for a reason. Different lubrication fluid and system but the principal is the same. It's rocket science heck anyone can do that, nuclear engineering however... Sorry old Nuc Engineer joke ;-)
While a small part of me wishes I still had access to the equipment to do a Spectrometric Oil Analysis on the ATF I'm going to go with change (drain and fill) it often is as critical as keeping it cool. No idea where Toyota came up with the lifetime fluid idea for the transmission but I'm not buying it. At all.
The factory OEM stat at 200° is way too high IMO and pretty sure CAFE standards have everything to do with that. Hopefully the Hayden stat will fully open at a much lower temperature.
While a small part of me wishes I still had access to the equipment to do a Spectrometric Oil Analysis on the ATF I'm going to go with change (drain and fill) it often is as critical as keeping it cool. No idea where Toyota came up with the lifetime fluid idea for the transmission but I'm not buying it. At all.
Running a transmission cold for extended periods of time is likely just a harmful as running at really high temps. There is an ideal operating range, and by pinning the thermostat on the trans you are taking away the ability for the transmission fluid to come up to temp as designed. Do you have any evidence to back your claims of the transmission temps being too high?
What would the operating temps of a transmission have to do with CAFE standards?
Send your trans fluid to blackstone for analysis.
Regarding lifetime fluid, I might not be correct, but I think the EPA dings auto manufacturers for selling products that require disposal of used fluids. But it says right in the owners manual that that all driveline fluids should be changed at 60k miles "if towing a trailer, using a car top carrier, or heavy vehicle loading".
Running a transmission cold for extended periods of time is likely just a harmful as running at really high temps. There is an ideal operating range, and by pinning the thermostat on the trans you are taking away the ability for the transmission fluid to come up to temp as designed. Do you have any evidence to back your claims of the transmission temps being too high?
What would the operating temps of a transmission have to do with CAFE standards?
Send your trans fluid to blackstone for analysis.
Regarding lifetime fluid, I might not be correct, but I think the EPA dings auto manufacturers for selling products that require disposal of used fluids. But it says right in the owners manual that that all driveline fluids should be changed at 60k miles "if towing a trailer, using a car top carrier, or heavy vehicle loading".
@jonshonda Like I said I went with the Hayden 698 because it has a stat, and hopefully will open at lower temps than factory 200°. Even if it isn't open until 170° that is plenty warm enough to be in the operational range of the ATF. And in the winter I always idle for ~10 minutes before engaging into gear. Likely get a ticket for that if I lived in some city. Evidence.... 20 years in the Navy Oil Analysis Program (NOAP) which eventually became the Joint Oil Analysis Program (JOAP) and machinery that cost in the millions of dollars. Each. Will that work?
The most common chart for transmission temps and range which is posted all over including here and on Mud is this one. Others are similar and in my experience I'd say it is very close.
Some have argued that it does not use synthetic ATF but I am OK with that as Toyota ATF WS is not synthetic.
Operating temps of transmission fluid have a LOT to do with CAFE standards. CAFE came out in 75 I was driving a 67 mustang with a 289 at the time. For decades CAFE never really had any teeth or had much of an impact but eventually it did. Now car manufactures have to pay $15 for every .1 mpg that they fail to meet the standard. Across the board for their fleet of vehicles, the GX falls under light truck CAFE standards. Why we are seeing so many turbos coming from Toyota and the last of the V8.
Most of the research done by the automakers is proprietary. But here is one done a few years ago "Investigation of Transmission Warming Technologies at Various Ambient Conditions," Society of Automotive Engineers Technical Paper. That 1.5-2.5% increase in fuel economy makes a big difference when you are trying to avoid CAFE penalties. The engineers are doing what the bean counters are telling them, not designing what they most likely would really do. But that is always the case isn't it? Scott Adams made a fortune with Dilbert depicting that fact.
Toyota does have exceptions to the lifetime statement but if you don't meet that criteria then they claim for the lifetime of the vehicle. Or as some have said until after the warranty runs out. Those that have had tranny issues usually don't tow or met any of the criteria for 60K service intervals. Picked up my 19 with 40K on it last Nov. and will do a simple drain and fill each Fall after towing. Until I hit 60K then I will drop the pan change the filter and do a complete drain and fill until all fluid is replaced. At that time I may sent a sample to Blackstone at least I would have a baseline. Right now not so much and it would have little meaning.
@jonshonda Like I said I went with the Hayden 698 because it has a stat, and hopefully will open at lower temps than factory 200°.
Again I have to wonder what the correlation between the transmission running at 200* and CAFE? Are you stating that there is a noted change in the viscosity of the transmission fluid at that operating temperature that would have measured effect on fuel economy? If that is the case, wouldn't you think both the fluid and transmission could be designed to operate effectively at those temps? You cannot use an across the board chart created by (insert company that isn't Aisin) and say it's the gold standard for every transmission. I'm not saying you are or aren't correct because I don't have the knowledge or facts to refute your opinion, but just because the transmission is running at 200* consistently doesn't mean it's wrong because some random chart says it is.
I am sure engineers are more then capable of designing a transmission that can be happy all day long at 200*. With that being said I did add the Hayden transmission cooler along with a complete fluid exchange at the dealership. My trans temp is consistently 165-170* when driving w/o increased load. When towing 4500lb brick of a camper with a cargo carrier full of fire wood, family of 4 and two 80lb yellow labs 180-190* with the occasional spike of 200*+ on hill climbs and such. I would suggest you top off the fluid and perform a level check to see if that has an impact on the temps.
04-16-24, 05:51 AM
