OK. Just what does the book say about towing?

Over on the Civil War thread about us 19-21 owners getting shorted a transmission cooler, there's off and on discussion or rather speculation regarding the use of drive or select shift when you tow.
Now I myself may have poured a little flammable liquid on this friendly chat myself by thinking my 21 manual species tow/haul and S4 when towing. Now I can only find mention of S4 when decending a grade. So, now I'm hiding out over here until things cool a bit in the cooler thread.

Can anyone find definitive proof one way or the other if towing in drive or S4 is noted in their manual?

 

Have not looked in the manual. My understanding is it references S4 for engine breaking.

What I did is tow my boat both ways and monitor the tranny temp in my 19. Hot summer weather, flat freeways, mixed hilly secondary roads, and just one steep grade. About 100 mi one way. For 95% of the towing I did, the key was the tow button. Temps were nearly the same D vs S4. If I climbed a longer grade, picking the right gear in S made sense temp wise.

Hope that helps.

 

Page 210 of the 2021 Tundra owners manual below.
● To maintain engine braking efficiency and charging system performance when using engine braking, do not use the transmission in D. Transmission shift range position must be in 4 in the S mode.

No specific mention of only using S while towing but it does mention a few pages further down that tow/haul should be used.

 

Keeping the cooler thread alive! Couldn't do it without ya

 

But I can also tell you from experience my 2016 gets better performance and MPG towing in S vs letting the truck shift. That way I can keep the rpm in the 2000-2300 range in s4 or s5, depending on terrain and my speed. Otherwise the trans is shifting gears more often and in and out of OD all the time, even on fairly light pulls (3000lb pop up). Towing in S is clearly easier on my truck and the better MPG and less shifting is proof enough for me.

 

That's all I can find too. I will say I've been bouncing between S4 and 5 towing a 5400# TT. Scangauge shows temps stay good but rise quickly when the TC unlocks in 5th. Also read (not in the manual) all the features of T/H may not be available when select shifting. On my trip home I may try D and T/H and see what the temps do.

 

I found a throttle position number on my scangauge. When in S5 and the TP reaches 35, I can drop to 4th right before the TC unlocks. I am concerned that maybe letting the TC unlock briefly before before the trans automatically drops to 4th may be better for the transmission even though the TC temps rises very briefly.

 

Ya'll do a lot of engine braking?

 

It is not about engine braking for me , it is about keeping the power/rpm in the sweet spot for what you are hauling/towing and auto shifting does not do that, it tries to keep lowest RPM, thus shifting around a bit and in and out of OD A LOT.

Tow something and play around with S/D towhaul, you will quickly see what feels best for your truck.

 

On the way to a campground in Mt View AR I found hills both up and down where S2 got some use. Narrow twisty two laners that made me wish I was in the 124 Abarth staying in motels.

 

Just for comparison sake, I run my F-250 with a 6.2L gasser in S4 with tow/haul engaged and it tows my TT great (I’m towing right around 11,000 lbs). I’d set yours to what works best for power and shifting - each tow load and terrain is different depending what and where you tow.

I won’t touch the trans cooler topic, this is just my experience with a completely different setup.

 

That seems to work for me so far. Been on the road for three weeks so yeah, I'm a real old hat at towing with a 4 week old Tundra and a two month old travel trailer
I am curious if anyone has found anything in their owners manual stating do not tow in drive. My wife thinks I'd be more comfortable dressed with shirts with pockets so I could use a pocket protector and keep a mechanical pencil and slide rule in it.

 

Previously I emailed Toyota with this exact question, as I didn't find the manual to be overly clear. I got an email back stating that Toyota's towing recommendation is to use T/H mode in D. Personally, I like to have a bit more control over the gears, so I generally use S mode, generally S5 and S4 as that's where my truck and trailer combo feel the best. I have towed in D, and it was just fine.

 

We are headed north on Friday from LA (lower Alabama) to Ohio and strong forecast crosswinds are to change to headwinds so T/H in D should be a good test. Ambient temps are to be about 10 to 15 degrees cooler so that will affect the readings. Full speed ahead and let the scangauge be your guide.

BTW, thanks for sharing the information.

 

This guy did the same and received a different response...
https://www.tundras.com/threads/transmission-cooler-missing…i-know-i-know.95783/page-19#post-2450441

 

How much you want to bet Courtney G drives a Pruis.

 

I saw that. It is pretty funny. My guess is whoever gets the question just researches it in the manual and provides their own interpretation of what's in the manual.

 

Manual says use S4 for grade braking. One thing I notice about the AB60 trans is it doesn't really downshift on it's own on grades like other modern transmissions do. On the flip side towing in D with Tow/Haul on it does hold gears and not upshift too fast. Mine spends most of it's time in 5th gear. The 6th gear in a Tundra is .58 and pretty high while 5th is .72 and more of a typical OD gear. I only use S mode when I know I'm going to be doing some downhill runs. The computer doesn't let the truck lug when in Tow/Haul mode so I don't bother using S mode when climbing.