19-22 Tundra Owners Transmission Important

@327Tundra doesn't have the retrofitted auxiliary cooler, so there wasn't any defect in an auxiliary cooler.

If he HAD retrofitted the cooler kit, I would suspect incorrect installation, blocked flow, or contamination of fluid as possible failure cause. In this case, all we're left with is @327Tundra bought a brand-new stock 2020 Tundra, and proceeded to use that truck for towing a nominal load (3000 pounds) DAILY except for weekends. His trailer weight was not even CLOSE to the TWR rating, but it was towed every day. Perhaps, that is like accelerated endurance testing that Toyota never applied.

The alternate conclusion, if failure cause wasn't fluid degradation due to high temperatures, is that Toyota turned out a transmission that lasted 20K miles under normal use. That makes even GM transmissions look good. I admit that every brand can have failures, but Toyota far fewer. I doubt this is an anomaly.

I expect we are going to see more data on this in the future. But, if I were using my Tundra for towing, I would not be in denial while waiting.

 

Good evening everyone just thought I’d give an update today was the first day back to work with the tundra and pulling the trailer at 3000 pounds loaded temperatures recorded at the pan registered between 239 and 259 all day today Does not look like this new transmission is going to even last 20,000 miles like their original I’m still in talks with Toyota corporate should have a final answer from them tomorrow I will keep you guys posted

 

Forgot to add outside temperatures today here in overcast Florida never got over 71° and my coolant temperature which literally stays at 195 to 197 No matter what outside conditions are but today I did see the coolant temperature spiked to 200 And my air intake temperature while moving never seen anything above 73°

 

Have you tried towing in s4?

 

that seems a tad high.

you need to find out if the hockey puck cooler was replaced or carried over to new transmission.

edit to add: someone should reflash the transmission tune to see if it’s holding torque converter out of lock up longer than normal.

 

I always tow in s4

 

Man those temps seem high. Has to be something else going on.

 

Doesn't the manual state otherwise? Tow/haul in D??

 

I did the same thing on my 19 Pro. Added and aftermarket transmission cooler with the Toyota thermostat. I bought two quarts of transmission fluid and barely used half of 1

 

Yep! I did this last year. I ended up making a thread on it which is still up. After everyone was arguing with me with all of the facts that I had obtained through TIS and the Toyota dealer itself I got tired of everyone complaining of every little bit. I tried to delete the thread but somehow moderators brought it back. But I'm locked out of the my very own thread now due to the moderators on this forum. But I went to a dealer, and got it all notated. Driving around on a 65 degree day, flat Terrain, normal Back Road highway speeds, and I was over 245 degrees. They said no problem at this time. I wasn't dealing with it, so I put on my own cooler

 

I'm petty sure they don't read the manual...they keep referencing S4 for the wrong reason.

I have the Setrab cooler kit but have not heard of how we will deal with moisture buildup in the trans fluid if temps never get above the point of moisture vaporization. I have not installed it yet. Milkshake trans fluid will also do damage...perhaps worse. I'm at 20,000 miles and thinking of doing more frequent transmission fluid changes as a preventitive measure.

 

Install the kit with the Toyota thermostat, leave the thermostat unpinned, and you will have no moisture problems.

The only way you can get "milkshake" fluid is if the existing warmer on the side of the transmission fails (unlikely) and coolant leaks across to transmission fluid side. Installing the kit would have no contributing effect on that failure one way or the other.

 

So then are we supposed to be using S4 or D? Manual kind of makes it seem like S4 is the preferred for heavy towing......and a large number of you guys on here suggest doing so.

Personally I was impressed with towing this RV using the Tundra. Felt stable. Did not sway. Did not spike transmission temps. Etc...etc....etc...

Thanks for any input.

 

Someone said in another thread that Tow/Haul does not work in shifter position "S". I have confirmed that is true from Toyota transmission literature (see below).

At the same time, I have found nothing in the Owner Manual that tells you what shifter position to use for towing. If Tow/Haul ONLY works in "D", then the implication is that towing in D is preferred.

On the other hand, placing the shifter in "S" also limits the transmission to an upper gear ratio, prevents un-necessary shifting, and cancels the AI-Shift function providing engine braking downhill. All of these functions may be desirable when towing.

My conclusion is the Owner Manual punts on this. If you are an experienced tow driver, S range probably makes more sense, especially if you are trying to minimize transmission fluid temperature. Towing in overdrive gears (S5, S6) could allow the inexperienced to overwork the drivetrain in terrain, but may work on flat terrain for the experienced driver. Transmission will downshift as necesary. S4 is safest for hilly or mountainous terrain because the transmission gear ratio is 1:1. With the Tundras low-ratio differentials, that will make your RPM higher than what you are used to, reduce your fuel efficiency, and may limit your speed.

 

Thanks for the response. That is interesting. My tow/haul button and associated lights suggesting it was in this mode stayed on despite rolling down the road in S4.

You did perceive or pick up the sensation of higher rpms at times.....which I assume was from the S4 deal more so than the tow/haul button being on.

When I pick my trailer back up I may try a test and see for 100 miles using D and tow/haul button engaged. Then go back to S4 and tow/haul button engaged. As for whether or not this tow/feature is somehow disengaged if in S4.......I couldn't tell because I had all indications that it was on or engaged.

 

It would seem to me that for an apple to apple comparison you would need to shift to S6.

 

From my 2019 owners manual...



Page 187

 

There's been a lot of discussion on that point here and a lot of us have concluded that it only applies when you're engine braking. So tow in D unless you're going down a steep hill.

 

Your point is if @327Tundra is using his truck for work purposes, Toyota would be justified in rejecting his warranty claim?

Yeah, that's under "Towing Tips", but I don't think you can read anymore in the tip than what it says, i.e. to "maintain engine braking efficiency" (if needed), and "charging system performance" (if marginal).

I believe what they're saying there is because of AI-Shift in "D", the truck is going to "coast" down hills without owner intervention. Engine RPM will be lower during coasting, maybe to idle in mountains, meaning MINIMAL engine braking until the foot brake is applied. Lower engine speed going downhill is also going to reduce alternator charging rate.

The last sentence about transmission shift position means IF you want to INSURE you have engine braking immediately available, and alternator RPM high, then the shifter must be in S4.

 

Try this for a test: Start towing in D, then shift to S (should go into S5 at highway speeds). THEN, push your Tow/Haul switch to see if the light on the dash comes on. The dash light should not come on.

Once turned on in D, the Tow/haul light on the dash may stay on in "S", but the Tow/haul function may not be active until the shifter is moved back to D.

 

The manual is very unclear in its recommendation regarding the use of S4 together with Tow/Haul.

As John175 wrote above, on page 187 of the manual the recommendation is to put the shifter into S4 - however, that is only one of many bullet points of "Trailer Towing Tips" and is contained in the bullet point regarding engine braking and charging system performance.

Then on page 189, in the section titled "Before Towing - Check that the following conditions are met:" the instruction is to "Depress Tow/Haul button. So here are

This leaves me with 2 questions:

• If S4 disengages Tow/Haul, then these two instructions are in conflict since both are recommended for use when towing. (Unless the recommendation is to only use S4 briefly for engine braking or enhanced charging.) Do we know for sure that S4 disengages Tow/Haul?
  
• If use of S4 is necessary to keep torque converter temperatures down when towing, and if S4 shuts off Tow/Haul, then what was Toyota's point in recommending the use of Tow/Haul when towing?

[EDIT: Sorry guys - I see a couple of new posts addressed this.]

 

I've tried driving up a hill in s5 then engaging towhaul and I could feel an obvious difference. To me towhaul works in s mode.

 

Whe you shift from d into s mode it defaults to s4 not s5. Not sure why Toyota decided on that, seems odd to me.

 

That would be contrary to the Owner Manual and the transmission document I referenced, but who knows...

It's been awhile since I played with S mode. S4 could be dramatic at high speeds. Makes me wonder if the transmission decides when S5 is the better gear.

The Owner Manual does say S4 or S5 for six speed transmissions, and S4 for five speed transmissions (?). Appears that the Owner Manual text gets reused year after year without corrections...like the window sticker spiel.

 

I’m a consumer so I wouldn’t use the word justified, but I’d guess they could. I read in another thread about rams being declined warranty for stuff like that. I know it’s a different company, but they’re all out to make money. Check your insurance. There is fine print there too like using your personal vehicle as a law enforcement vehicle isn’t covered. Another thread talked about how the tundra is a passenger vehicle, not a commercial vehicle.

 

Exactly

 

A Blackstone report of a friends ATF after 55k miles of good use/abuse on his MY19in AZ showed no indication that anything abnormal.

And as noted previously, the puck is labeled as a cooler. So your arguement is literally invalid to argue that the "vehicle is not equipped with an ATF cooler".

To make a valid arguement, you'll need evidence that the cooling puck does not provide sufficient cooling to keep up with the demands/loads the truck is listed for therfor causing premature failure. Some field failures woud very much help build your case.

 

I fix! NOW!!

 

But his 2018 has the auxiliary cooler that the 2019+s don't.

 

Fat finger sorry, been fixed.
MY19