'Tow/Haul' vs 'D' vs 'S' when towing

What do you prefer when towing?
- Tow/Haul
- Regular D mode
- S mode (selectable range)

I've always used D, never Tow/haul, but it seems many here like TH mode. On downhills I go to S and downshift, but then return to D.

 

Usually THD, sometimes THS if necessary

 

I would agree with @14burrito I've towed in and out of El Centro and up towards Reno, NV from Arizona where the inclines are sometimes massive and the gear hunting made me feel like it would overwork the transmission and overheat it, so I'll hold the THS in 3rd and upshift and downshift as necessary... I don't tow often, but when I do its usually THS, LOL...

 

I think when using tow/haul you need to be in drive. I think moving to S while in tow/haul deactivates the tow/haul features.

 

Pretty much always th
Drive much of time as load was usually light 2-3k and honestly I wasn’t as familiar w towing using s. I looked into further ahead of renting a bobcat and trailer, about 6-7k.
Ths4 when hauling that heavy load through city and then highway to keep from shifting around in the od gears on the highway

Finally got an OBD to check out Tran temps but haven’t towed yet since

 

Does not. I tow my bay boat with TH and generally in 5th

 

Tow haul in drive. The only time I would switch it to S is if it were constantly shifting on hills or I wanted to downshift on a long downhill. To be honest, the computer that does the shifting knows more about what gear the truck should be in than 95% of the drivers out there.

 

Tow/Haul, always in D since the addition of the trans cooler, as mentioned in S mode on steeeeeeep inclines.

 

I drive in S mode all the time, and I don't tow anything.

 

Some without trans coolers have had pretty good success managing transmission temps using Tow/Haul and S4 as the manual mentions to keep it out of overdrive

 

My transmission temperatures went way up in D, always towed in S and mostly stayed in 4th gear.

 

When pulling my #7500 Jayco, T/H in S4. When towing something in the 2-3k range I can get away with S5 in my non-mountainous area. I monitor tranny pan, t/c output, engine oil, and coolant temps with a scanner while towing and here's what I've noticed.

The key to keeping tranny temps down is having the torque converter locked up. The minute it unlocks, with a load or without, the t/c output temp immediately increases 5-15 degrees. Add a hill and/or a load and it goes up from there. The minute it locks back up that temp will drop back down and equalize with the pan temp and I'm assuming that it's dumping it back into the pan which will then come to equilibrium with the rest of the system. With a constant locking/unlocking of the t/c the pan, engine oil, and coolant temps will all creep up together with the t/c output as the main source of heat.

Even with the 7500# Jayco on the back (no lectures, I weigh my stuff every trip and know exactly where I'm at) S4 does a really good job of keeping the converter locked up. Yes, there's some extra revs involved but the engine is perfectly happy there.

 

This. ^^^^

I've even gained a MPG driving in S vs. D.
Went from 11.3 to 12.5( nannies off/beast mode). 37's on 4.30 gears....from my last fill up

 

This is what I’m referring to. The Manual does say to use S mode if you need to maintain engine braking or charging performance. But I think the tow/haul mode uses the AI shifting which says is disabled in when in S mode per the manual.

 

I've towed a 5,000lb boat and trailer on TH in D and just in D only. I notice the TH changes the shift points, but never had a prob with increased temps even after an hour towing.

 

When towing, I always run Tow Haul in S4 or perhaps S5 in very flat terrain. I monitor trans temps and see exactly the same thing as @NorthWoodsTundra . I have the air transfer trans cooler but still see the same effect.

 

I live in hilly terrain and always tow in s4 with T/H mode.

 

Like Northwoodstundra and Buckaroo I tow in S5 and Tow Haul. I monitor my transmission temps and when I hit a hill and the temp starts climbing, I down shift to maintain an acceptable transmission temp.

 

So in other words:
1) You get in the car
2) Put transmission into D
3) Press Tow/Haul, thinking you're now in Tow/Haul (you are)
4) Put transmission into S, thinking you're still in Tow/Haul (you're not...)

You can only be in THD or S, it seems. There is no THS. That's the way it should be since 'S' implies that you want manual control.

 

T/H and S are separate but can be used in conjunction with each other.

In S you are not manually shifting, but limiting it to what you select. If you select S4 it will shift normally but not go past 4th gear.

Tow/Haul remaps the shift points and will allow more revs before upshifting and will also downshift more aggressively.

 

I think he’s meaning that once you shift into S mode that now your tow/haul shift points are now back to normal shift points. So if you put it in tow/haul and S4 going up a mountain pass then your TH shift points are back to normal shift points.

the way I’m reading the owners manual it sounds like you would be in TH and in D for going uphill or downhill so the shift points in TH can help you. And you can leave it in TH and put it in S mode when needing more engine braking or you’re running on fairly flat ground where you want to keep it in its optimal RPM range. It seems you can have TH mode and S mode on at the same time but The AI shift points only work while in D.

 

Well now I have to go test it, lol. Without being able to point to any reference I'm pretty sure I noticed a difference in shift points between T/H on or off both while in S4.

Good excuse for a coffee run this morning. ☕️

 

Haha ya I’ll have to test this tomorrow on my way to work also. That’s just what I’m picking up from reading the manual. Seems like TH using AI shifting and AI shifting only work in D. But a test in the name of science is needed I think

 

So I did a deep dive into the FSM and found this little tidbit. Seems to indicate that TH is only active in D. Not what I expected.

DESCRIPTION
The ECM receives tow/haul pattern select switch information and performs the tow/haul control.
While the tow/haul control is operating, in contrast to normal mode, low gears are used to increase engine
braking and towing power, reduce frequent shifts, and improve driveability. The tow/haul control includes throttle
control, shift schedule control, wide open throttle shift timing control and AI-SHIFT control.
Tow/haul mode only operates when the shift lever is in the D position and the tow/haul pattern select switch is
ON.
HINT:
The tow/haul pattern select switch is a momentary-type switch.
In order to cancel tow/haul mode, push the tow/haul pattern select switch again or turn the ignition switch
off​

Regarding the age old question about how high is too high for ATF Temps, I found another tidbit. It seems that the A/T Temp warning light comes on when the fluid reaches 302F and goes out when it comes down to 275F. It says the temp sensor that the ECM is acting upon is Sensor No. 2, located on the transmission, just in front of the oil cooler inlet pipeline - trans pan or torque convertor?

 

Nice, this is the same info I found in the manual.

 

Seems pretty clear there. Thanks!

 

Not that I can dispute the FSM, but when I tow in S5 with Tow Haul engaged, I notice different shift points. On hills when accelerating, I often find myself modulating the accelerator to allow an up shift. The problem I have is that in D, my tranny temps are too high. If I use S, then I can manually shift and maintain acceptable Tranny temps. I would love to just use D.............

 

That's because you shift with GEARS instead of the throttle.

 

There was probably a time when I drove my Tundra in "D" but it's been so long ago, I forget.