20K and ATF Degradation @ 65,000

I don't believe the transmission goes into safe mode unless one of the following happens, malfunction of: Input Speed Sensor, Output Speed Sensor, ATF Temp Sensor 1, Solenoid Valve S1-S4 and SR, Solenoid Valve SL1/SL2, Solenoid Valve SLU/SLT. The first three prohibit gears 5-6.

I'm curious on the protocol it uses for raising the number, but this "estimate" is just that, an estimate. Our Sequoia's been maxed out for a while and no issues.

 

Oh yeah, it does. At 150 C the temp sensors are out of range, it switches over to a preprogrammed ATF temperature, because it can not trust the input anymore. In some TCM firmware modification it does the switch permanently after a few overheating events.

I read my Tundra today and found the counter to be 2660. D&F it 2 times, the first one was of brown color, which indicates burnt fluid.

 

I should have been more clear. Please see my post #17 that supports below. I'll add my opinion, it exists for a reason and I'm not convinced it should be ignored. If nothing else, it's a tool available to help manage maintenance appropriately.

Updated/clarifying details: Last complete fluid replacement and reset was 15k ago, drain and fill about 7k ago (no reset). Towing duty is nearly 50% of all mileage.

 

The degradation value on my 2016 Tundra was pegged at 65, 650 which I believe is the highest value it will display and the truck only has 20,000 miles on it. When the degradation value is reset the transmission supposedly changes the shift pattern. The transmission adjust depending on the condition of the fluid.

 

To clarify, I'm not talking about simple adjustments to shift pattern, but the fail-safe mode that disables 5th and 6th gears, AI shift control and so on, which I don't believe the counter affects. That's what I've known "safe" mode to be in transmissions.

 

I believe the degradation value is based on time, mileage and transmission temperature history.

 

@Ruggybuggy you consider running a Blackstone analysis when you change it? I'm going to run one just for the heck of it on our Sequoia and Tundra.

 

If it was something that was available and cheap I might but I'm in a rual part of Canada and shipping is expensive. I'm not overly concerned about it. The AB60F is a very reliable unit even when abused.

 

Checked my 2020 this morning with 33k miles and it’s days 2235. The manual talks about short trips below 32 degrees being severe driving conditions, so maybe that accelerates it. I live in the Louisiana and have the ATF cooler installed.

 

For engine - yes (water condensation and gas in oil). For transmission - not so much.

 

here's a semi-relevant question:

I pinned my thermostat open.

instead of running ~195 degrees, I now run at 165-ish degrees.

is this lower temp good or bad for the transmission?

 

In Texas it is good. Can be slightly worse in winter up north in Canada, but they tend to run electric heaters anyway.

I run additional cooler after stock heat exchanger in my Volvo, the temps are 120 to 180, depending on the season. ATF becomes dull over time (slip additives consumed), but never dirty. I replace ATF only to replenish additives. You should be doing that, too.

 

i drain and fill every 30k....or thereabouts.

for those exact reasons you mention. <hat tip>

 

It's horrible... like adding sand to your personal lubricant.

 

No, unpin it. The transmission in the Tundra is designed to run around 195 and running it at a lower temperature is not the best thing. For some reason some members think pinning the thermostat open will prevent the transmission from over heating. Once the thermostat is open, it's open and all the fluid is directed to the ambient cooler (if you have one) so pinning it open doesn't do anything but prevent the transmission from getting to its designed operating temperature. Toyota designed the system so it maintains a constant temp.

 

Along with 0w20, thin and unnecessary heated ATF are there only to reduce pump losses by 0.5% and please EPA functioners. For lubricity, pressure buildup and heat resistant thick fluid is best.

TCM has viscosity-temperature tables in software and shifts adaptations as well.

 

Sorry man but everything you said is bad advice. The transmission is designed to run at a specific temp and running it at a lower temp can cause issues. Yes we do have electric block heaters but they do nothing in regards to warming up the transmission. Never add additives to your transmission. Just do a drain and fill every 6 years or 60,000 miles.

 

Could elaborate on specific issues you've mentioned?

 

Well I guess your smarter then the engineers that designed the transmission? This is not a new transmission and has been around since 2007. The trans fluid has always been WS fluid with no changes in the viscosity. We are still using the same transmission in 2021 and still using the same WS fluid. It's a very reliable transmission and next to nothing for problems. Why mess with something that hasn't show any problems?

 

Because your temperature in July is less than they may have in October in Texas. Because you may prolong the transmission's life even further.

So, what about explaining the issues you've mentioned? Without resorting to talks that some engineers are smarter than others? I can give a few ideas of what can go wrong in the transmission at super cold temps, but they are not ever happening in Texas.

 

The torque convert clutch will not engage as often, moisture build up, lost fuel economy and shift pattern will be modified for the cooler trans temps.

 

Go run your idea to any Toyota tech and you will get the same answer. Don't pin your thermostat. You gain nothing by doing it. Again, when the thermostat opens, it's open. The fluid is now directed to your ambient cooler. Pinning it open does nothing but prolong the transmission from reaching operating temperature even in Texas.

 

You say the TC will be not locking up at 165F? Have you at least verified it yourself to stand behind your claim?

The transmission is sealed, water has no way entering it in quantitative numbers.

Fuel economy at 165F is actually a bit better than at 195F, because unlocked torque converter performs slightly more efficiently with more viscous fluid. The colder the fluid the more viscosity it has.

Pumping loss is negligible.

Replace WS (cSt@100 around 6.8) with older T-IV (cSt@100 around 7.2) and you feel how much harder it pulls. No, it will not break.

 

I never said the TC wouldn't lock. I said it won't lock as often.

I'm done. Go live with your pinned transmission. You gain nothing from pinning the transmission but obviously you are hell bent on it.

 

No, I'm theoretically educated on that topic and generally arrogant to any blind faith not backed good by knowledge.

My Tundra's t-stat is not pinned. It sees winters. But I keep the pin in the glovebox.

 

anecdotally

I've had it pinned for a couple months

I have not seen any difference in mileage or performance. other than ~25 degrees cooler.

and since I run a S/C, I like things to be cooler.

however; If we get a cold front & I see the operating temps stay lower than 120, I'll un-pin it.

I made up the 120. It's my number. nobody elses.

 

I would do 124 as your limit.

 

Science!