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The other night I was going up an incredibly steep gravel back road with my truck. It's steep enough that you cannot make it up the hill without being in 4wd. With that being said, it does receive quite a bit of travel because it's a mountain pass that is a short cut between two counties, so it's not some rigorous trail. I didn't have a trailer hooked up, but it still requires quite a lot of torque to make it up the mountain. I had to travel the path twice that night and the first time up, I wasn't using tow/haul mode and kept it in 2nd gear using the "s" mode, and when I got to the top I could smell that typical smell you get when your transmission is hot. The second time up, I used tow/haul mode and didn't get any smells or signs of heat. Does tow/haul mode lock the torque converter? I've heard so many different answers to that question, and to what tow/haul does in general.
 

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The attached file is an old document on the Gen2 Tundra transmission. On pp. 35-37 it explains what tow/haul mode does. I suspect that the only way it would promote transmission cooling in a slow-speed hill-climb situation would be if it forced you into a lower gear than you would otherwise be using. At least on the early years, it is only active in "D" mode; it does nothing when the shifter is in "S" mode.

Also I believe the torque converter only locks up in 4th gear or higher. So on a low speed hill climb, the only way you could possibly get into 4th gear to minimize transmission heating would be to use 4Lo. If not using 4Lo, S-1 would be advised to keep rpms as high as possible to minimize slippage in the torque convertor and to maximize coolant and ATF flow rates to promote cooling of the engine and transmission.

On my truck, I don't smell anything when the transmission gets hot. See:

http://www.tundratalk.net/forums/tundra-drivetrain/693442-low-speed-transmission-overheating-documented.html

EDIT: Correction - the torque converter will also lock-up in 3rd gear. Here's a quote from the 6-speed transmission document:

Flex Lock-up Clutch Control
In the low-to-mid-speed range, this flex lock-up clutch control regulates the solenoid valve SLU to provide an intermediate mode between the ON/OFF operation of the lock-up clutch in order to improve the energy transmitting efficiency in this range. As a result, the operating range of the lock-up clutch has been increased and fuel economy has been improved. The flex lock-up clutch control operates in the 3rd, 4th, 5th and 6th gears in the D position and S6 range, 3rd, 4th and 5th gears in the S5 range, 3rd and 4th gear in the S4 range. Even when the vehicle is decelerating (the accelerator pedal is released), the flex lock-up clutch control operates. Therefore, fuel-cut area of the engine has been expanded and fuel-economy has been improved.
 

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Discussion Starter #3
The attached file is an old document on the Gen2 Tundra transmission. On pp. 35-37 it explains what tow/haul mode does. I suspect that the only way it would promote transmission cooling in a slow-speed hill-climb situation would be if it forced you into a lower gear than you would otherwise be using. At least on the early years, it is only active in "D" mode; it does nothing when the shifter is in "S" mode.

Also I believe the torque converter only locks up in 4th gear or higher. So on a low speed hill climb, the only way you could possibly get into 4th gear to minimize transmission heating would be to use 4Lo. If not using 4Lo, S-1 would be advised to keep rpms as high as possible to minimize slippage in the torque convertor and to maximize coolant and ATF flow rates to promote cooling of the engine and transmission.

On my truck, I don't smell anything when the transmission gets hot. See:

http://www.tundratalk.net/forums/tundra-drivetrain/693442-low-speed-transmission-overheating-documented.html
You sure? Because when going up a second time, I had the vehicle locked in 2nd using the "S" mode and I felt a noticeable boost in torque when I hit the tow/haul button.
 

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You sure? Because when going up a second time, I had the vehicle locked in 2nd using the "S" mode and I felt a noticeable boost in torque when I hit the tow/haul button.
@Jswai144, you didn't read @MtnClimber's referenced thread, did you? If you had, you wouldn't be asking that question. I'm virtually certain that if he's answered your question, you can believe the answer. If you take his driving advice, the answer will be academic anyway. ;)

@MtnClimber has taken the time to answer and document this question for himself, for you, or anyone else with similar terrain. It answers how Toyota Tundra/Sequoia owners should drive their vehicles under these conditions to avoid transmission overheating. It is the most intelligent and comprehensive study I have EVER seen on an internet forum; the pity is this thread was viewed by so few and had only one follow-up post. :(

@MtnClimber, that study is an outstanding contribution IMO. And, with a 4.6L too; I am impressed...you clearly do not take "NO" as an answer from your "little V8". BTW, that looks like the country north of Las Cruces, NM.
 

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You sure? Because when going up a second time, I had the vehicle locked in 2nd using the "S" mode and I felt a noticeable boost in torque when I hit the tow/haul button.
What year and model of truck do you have? Since Tow/Haul is implemented via software, it is entirely possible that later years have a working Tow/Haul in S-Mode. As far as I can tell, on my 2012 Tow/Haul doesn't do anything in S.

Here's one way you might be able to test. When lugging up a moderate hill on the interstate in 6th gear in "D," hitting Tow/Haul immediately initiates a downshift to 5th (without any change in pedal input). My truck doesn't seem to do that under the same conditions in S-6.
 

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What year and model of truck do you have? Since Tow/Haul is implemented via software, it is entirely possible that later years have a working Tow/Haul in S-Mode. As far as I can tell, on my 2012 Tow/Haul doesn't do anything in S.

Here's one way you might be able to test. When lugging up a moderate hill on the interstate in 6th gear in "D," hitting Tow/Haul immediately initiates a downshift to 5th (without any change in pedal input). My truck doesn't seem to do that under the same conditions in S-6.
It's a 2016, so maybe the software did change? Either way, thanks for being helpful and not a smart ass douche like the other guy.
 

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It's a 2016, so maybe the software did change? Either way, thanks for being helpful and not a smart ass douche like the other guy.
That's what you get, OldGuy43 for expecting people to comprehend.
 

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That's what you get, OldGuy43 for expecting people to comprehend.
No, I didn't say what I said because I'm mad that I "don't comprehend" or whatever. I said what I said because my comment/quote wasn't directed towards @OldGuy43, and he chimes in with a smug and snarky remark. Funny thing is, I don't think he paid attention to the context of my question when I asked "You sure?...." I wasn't questioning MtnClimber's entire post/analysis, but questioning whether or not "S" mode cancelled out the effects of tow/haul. Then OldGuy43 comes in asking if I read the referenced post in a not at all friendly way, when in fact, I did read the post and it had virtually nothing about whether or not tow/haul mode was cancelled out by putting it into "S" mode. Once again, the reason I asked if @MtnClimber was sure about the cancelling effect was because he mentioned it in a comment on my post, and I was replying, because this is a forum and you converse to reach a conclusion or goal of understanding. I made the post for my own understanding and possible future knowledge for anyone that reads the post. OldGuy43 is not obligated to read or respond to the post if he does not wish to, and probably shouldn't if it's going to bother him and he's going to bring a negative attitude into a previously friendly thread by responding without paying any attention to context at all. That goes for you as well. There's no sense in bringing hostility into a civil conversation just because someone doesn't "comprehend" something. I don't care if you're a senior member and pull the seniority card either. We are all human beings and should be able to treat one another with a bit of respect and compassion.
 

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No, I didn't say what I said because I'm mad that I "don't comprehend" or whatever. I said what I said because my comment/quote wasn't directed towards @OldGuy43, and he chimes in with a smug and snarky remark. Funny thing is, I don't think he paid attention to the context of my question when I asked "You sure?...." I wasn't questioning MtnClimber's entire post/analysis, but questioning whether or not "S" mode cancelled out the effects of tow/haul. Then OldGuy43 comes in asking if I read the referenced post in a not at all friendly way, when in fact, I did read the post and it had virtually nothing about whether or not tow/haul mode was cancelled out by putting it into "S" mode. Once again, the reason I asked if @MtnClimber was sure about the cancelling effect was because he mentioned it in a comment on my post, and I was replying, because this is a forum and you converse to reach a conclusion or goal of understanding. I made the post for my own understanding and possible future knowledge for anyone that reads the post. OldGuy43 is not obligated to read or respond to the post if he does not wish to, and probably shouldn't if it's going to bother him and he's going to bring a negative attitude into a previously friendly thread by responding without paying any attention to context at all. That goes for you as well. There's no sense in bringing hostility into a civil conversation just because someone doesn't "comprehend" something. I don't care if you're a senior member and pull the seniority card either. We are all human beings and should be able to treat one another with a bit of respect and compassion.
Thanks, I'll be over here in the corner in timeout for a while.
 

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No, I didn't say what I said because I'm mad that I "don't comprehend" or whatever. I said what I said because my comment/quote wasn't directed towards @OldGuy43, and he chimes in with a smug and snarky remark. Funny thing is, I don't think he paid attention to the context of my question when I asked "You sure?...." I wasn't questioning MtnClimber's entire post/analysis, but questioning whether or not "S" mode cancelled out the effects of tow/haul. Then OldGuy43 comes in asking if I read the referenced post in a not at all friendly way, when in fact, I did read the post and it had virtually nothing about whether or not tow/haul mode was cancelled out by putting it into "S" mode. Once again, the reason I asked if @MtnClimber was sure about the cancelling effect was because he mentioned it in a comment on my post, and I was replying, because this is a forum and you converse to reach a conclusion or goal of understanding. I made the post for my own understanding and possible future knowledge for anyone that reads the post. OldGuy43 is not obligated to read or respond to the post if he does not wish to, and probably shouldn't if it's going to bother him and he's going to bring a negative attitude into a previously friendly thread by responding without paying any attention to context at all. That goes for you as well. There's no sense in bringing hostility into a civil conversation(FYI dude, you started the name calling, so your definition of civil is wacked) just because someone doesn't "comprehend" something. I don't care if you're a senior member and pull the seniority card either. We are all human beings and should be able to treat one another with a bit of respect and compassion.
Is this Lee's Rig's other account?
 

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Tow/haul mode on the 2.5 gen trucks changed the ramp speed of the pedal vs throttle plate.


You can find this out if you don't believe me by searching "Tow/haul mode" ...


Newer gen has a softer throttle ramp rate vs the older trucks.


the 2nd gens had a touchy pedal, and they changed that via software, but when you push tow/haul it changed back to a more quick throttle ramp.



Remember, it is all drive by wire as far as throttle goes...
 

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Hoping to get to the OP's point...my answer is NO. Tow/Haul mode really has no benefit or use for your situation.

If it were me, I'd do the same thing. 1st or 2nd gear in S mode the whole way...but I would not consider the T/H button if I was not towing.

I would however, consider driving in 4LO based on the description. Hell, I was 4LO on some well paved winding trails (gravel and asphalt...2 different trails) in the Smoky's with great results. Why not try it?
 

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Thanks, I'll be over here in the corner in timeout for a while.
Sorry, @NoKenDo, I regret that my actions have led to you're getting vitrioled, but thanks for the support. I kept going over it in my head wondering if it was (1) my telling him hadn't read the thread, or (2) my telling him he hadn't understand what was written there that had pizzed him off. I must have used wrong words...must work on including charm in my delivery if I want to keep this job. Un-subbing this one now. :(
 

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Discussion Starter #14
Hoping to get to the OP's point...my answer is NO. Tow/Haul mode really has no benefit or use for your situation.

If it were me, I'd do the same thing. 1st or 2nd gear in S mode the whole way...but I would not consider the T/H button if I was not towing.

I would however, consider driving in 4LO based on the description. Hell, I was 4LO on some well paved winding trails (gravel and asphalt...2 different trails) in the Smoky's with great results. Why not try it?
Thanks for the constructive comment. I'll just try 1st gear or 4lo next time. Only reason I didn't use 4lo is because of how bad axle bind is when turning with these heavy trucks haha.
 
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