# Tow / Haul Mode Question



## Insomniak (Jul 7, 2006)

This is my first experience with a vehicle that has a "tow / haul" button, and I'm not sure if I really need to use it.

The Tundra has a six speed transmission, and it's geared pretty low in the first couple of gears (kinda like what we used to call "Granny Gear" many moons ago...). When I put it into tow/haul mode, it seems to wind the engine up pretty good before it shifts to the next gear, and when I slow down it holds that gear longer to provide engine braking.

I know that it's doing what it's supposed to do, but when I take tow/haul mode off, the truck seems to do just fine pulling the 28RSDS.

Can I just selectively use the mode when I need to, like on big hills, or should I leave it on all the time when I'm towing? There's no overdrive button to keep the transmission from going into 6th gear, if that helps.

Just another one of my 3am














moments !!


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## Thor (Apr 7, 2004)

I am not sure how the mode works on your truck with a GM it does the following:

When activated for trailering or driving in the mountains, this feature reprograms the automatic transmission. The Tow/Haul mode feature changes the shift schedule to help reduce the frequency and improve the predictability of transmission shifts

This is what I found on the website

TOW/haul mode

Most GMC trucks equipped with an automatic transmission feature a Tow/Haul mode, which helps minimize wear and tear on the transmission by reducing the frequency of transmission shifting when pulling a heavy trailer. It also improves performance and control of your vehicle's speed, for smoother operation.

Pressing the Tow/Haul mode selector switch located on the end of the gearshift lever produces a more aggressive shift pattern, which lengthens the shift intervals and produces firmer upshifts

Thor


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## freefaller25 (Mar 19, 2006)

I would follow what is written in the owner's guide. There are likely other aspects to the tow haul mode like increased line pressure on the clutches and earlier torque converter lockup. Both will help limit the wear and heat in the transmission under higher loads.

Tony


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## RizFam (Feb 25, 2006)

I initiate the Tow/Haul mode every time I tow. I can really feel the difference it tows much more smoothly. I suggest you use it.







I tested the feature initially just to see if I could notice a difference & it was a remarkable difference, I thought so anyway.

Good Luck,
Tami

PS) How are all of those Mods going? Inquiring minds want to know.


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## wolfwood (Sep 19, 2005)

I agree with everyone else and for all the same reasons! The engine/tranny are designed for towing with the Tow/Haul Mode on and the wear/tear will be minimized. Will it tow w/out T/H on? Sure it will, but I LOVE MY TUNDRA and want it around - and healthy - for a lonnnnnnngggggggg time.

btw, we do have the ability to keep the engine out of OD.

Drop the stick into "S" (or "Shift") mode and look at the Tach. You should see a small window on the lower right side (of the Tach) with a number (probably '6'). Bump the stick back and that number will change to '5', bump it back again and it will change to '4' (bump it forward and it will change back to '5'). This sets the max gear that it will shift into. As '6' is OD, set it at a max of '5' when towing on the flat.....adjust down (then up, again....but less than '6') depending on terrain & desired torgue.

With the truck in Tow/Haul & Shift mode set at max '3', we floated down a 10mile 9% grade and I never  touched the brakes! The truck did exactly what it was supposed to and all sensors kept us level and in control (at about 30mph) !!!


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## NJMikeC (Mar 29, 2006)

Insomniak

Freefaller is going along the right path. Every shift has a little slip (wear) and with the added weight of towing there is a little bit more of a slip. For longevity use Tow\haul. Especially considering that that particular transmission is "new" and hasn't stood the test of time. Your also probably increasing the life of the trans fluid by using it.

Additionally and here is where you should do some further research the Tow\haul is likely to lock up the torque converter earlier and keep it locked even up to 6th gear. Locking the torque converter provides the advantage (as close as possible) of a manual coupling of the converter. That coupling reduces power loss. The power loss appears as heat so your allowing increased power at decreased temps when the torque converter is locked. I suppose you should stroll to Tundra Solutions as some of those guys may have the real low down on that trans.

Now I'm going to think out loud. I actually don't like that 4.30 rear end linked to a six-speed trans. The 4.30 says run at higher RPM and pull hard. The 6-speed says no go to lower RPM for Gas mileage thereby creating very small shift windows. Tow haul makes those windows wider. I suspect that Judi is correct to run at 5th in tow-haul, everywhere. I could easily envision many roads such as here in the Northeast that you can run at 50MPH yet they are up and down and around a million hills and curves. That trans would likely get really busy and start to make ya nuts. Tow\hauls should clean some of that up for ya.

Mike C


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## jlukens (Oct 3, 2006)

I have a GMC 6.0L and I use BOTH the tow/haul mode and shift into D3.


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## NDJollyMon (Aug 22, 2003)

I always use it on the TITAN.


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## wolfwood (Sep 19, 2005)

SconnieJonny said:


> I have a GMC 6.0L and I use BOTH the tow/haul mode and shift into D3.


Yes - BOTH!


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## Insomniak (Jul 7, 2006)

Thanks for the replies everybody. I'll just use tow mode when I'm supposed to - when I'm towing! Sometimes the brain asks weird questions in the middle of the night.....

Gonna be posting pics from all the mods that are now FINISHED - whoo hoo !!


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## Carey (Mar 6, 2012)

Agree with everyone else. Just use it anytime you tow...

I use mine frequently when the truck is empty, not towing, and going down steep mountains. I use a combo of overdrive off, and tow haul, depending on terrain downhill.. That way I use the brakes much less going down mountains.. Works great!

Carey


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## wolfwood (Sep 19, 2005)

NJMikeC said:


> ...... I suspect that Judi is correct to run at 5th in tow-haul, everywhere. I could easily envision many roads such as here in the Northeast that you can run at 50MPH yet they are up and down and around a million hills and curves. That trans would likely get really busy and start to make ya nuts. Tow\hauls should clean some of that up for ya.


Hey Mike, not to disagree with you....especially when you're saying I actually "might" be right...but setting the Shift Mode at "5" doesn't necessarily mean I'm IN 5th gear...it just means I won't go into 6th/OD. Just as setting it at "3" means it won't shift into 4th, 5th, or 6th.


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## Insomniak (Jul 7, 2006)

Thanks for the tip about the transmission Wolfie. I haven't messed with it much, other than putting it in "D" and just....driving! I was thinking that setting it to say, "5" meant you're in 5th gear and that's it. On the way to work tonight I tried it out, and setting it to 3, 4, or 5 means that's your maximum gear, but it still downshifts when you slow down or stop.

Another day, another couple brain cells.....


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## mjwencl (Feb 25, 2004)

I've noticed lately that if I use Tow/Haul using Overdrive that I'd best not use cruise control. I manual pedal the throttle. That way I anticipate the hills better than cruise control ever can. Don't think cruise control can see very well down the road anyway when it's a little hilly.

When I'm traveling under 60 miles per hour and want to use cruise control, then I shift into (3) and leave it there. Mileage seems to be better in (3) and the tranny is happier too by not running the RPM's too low.

My two cents...

Cheers,
Michael


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## Rubrhammer (Nov 27, 2006)

The manual for my Silverado said that Tow/haul is most effective whencombined weight is _at least_ 75% of GCVW.
It won't hurt you to run it at any time though. I use it when in rolling hills or a head wind. Other that that the truck doesn't seem to need it. On secondary roads I would never get into OD with it on. 
You'll know when if the tranny keeps hunting for a gear it likes.
Bob


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## ron4jon (Sep 26, 2005)

This May, we made a trip to Destin, FL which our first "long" distance trip with this TV & TT combination so I had to experiment to find the best performance both for keeping up with traffic and maintaining fairly constant speed over hills and hoping to mimize fuel burn rates. 2/3 of the miles were on I-65 with the rest on secondary state and US highways. Going down, I drove mainly in D3 with cruise control sometimes. Coming back home (same route) I used tow mode and didn't use cruise very much because the tow mode in cruse control was not pleasant and engine rpm seemed too high. However, much to my surprise the fuel consumption was better at 9.5 mpg coming back in tow mode versus 9 mpg going down in D3 mode! The only thing I can think of that was a contributing factor is that my personal control of the throttle up and over hills resulted in fewer kick downs and less sever throttle swings. Total time from point to point was about the same â€" 7 hours and 340 miles each way and same number of potty and gas breaks. So I plan on using tow mode every time I pull our 28FRLS 5er.

One bummer is that the TVâ€™s 8.1L drank almost a quart of oil each way (Mobile One 5-30)! It has only 17k miles and doesnâ€™t do this around town. I have only had this 2004 GMC Â¾ TV for a year and therefore have only made short trips up until the FL trip. I have put only 2k miles on this TV within a 50 mile radius of home this past year with only 1/5 of the miles towing the TT.


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## Mgonzo2u (Aug 3, 2004)

The wind was at your back on the way home.


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## Rubrhammer (Nov 27, 2006)

Cruise control is not noted for its ability to conserve fuel. You are spot on that you can and do anticipate hills better than it can. I never use cruise while towing for that reason. Maybe on the flats it would be alright.
Bob


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## 3LEES (Feb 18, 2006)

ron4jon said:


> This May, we made a trip to Destin, FL which our first "long" distance trip with this TV & TT combination


Now that you know the way, how about joining us for the 2008 Southeastern Outbacker Summer Rally?

We had a blast last year, and this year looks like it'll be better than ever!

Registration is now open. Click on the above link and follow the instructions.

Hope to see you there!


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## NJMikeC (Mar 29, 2006)

Ron4jon,

Stay in tow/haul mode and cruise as well. The trans may be still learning and if it acts like the DMAX/Allison it will learn to be less busy. I used to have a hard time getting the Allison to go into 6th when in Tow/haul but no longer. Once the road flattens it settles right in. I have a little bit more motor but even try it in 5th. D3 is too low in my opinion and you have a strong motor.

Mike C


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