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

That's good intel. I'm glad to see that I was way below warning temps when I towed a camper up an incline to 4000'. My trans reached 221° at the pan and 246° at torque converter. And it was only for a moment

 

Working on some tuning tweaks, figured I’d share for those curious about how it works.

Throttle for normal and tow/haul



Shift scheduling



Torque converter lock and release



Flex apply and release for normal/s6, the other is s1-5.

 

I went and did a test drive and the it still seems to be in tow/haul mode even when I would switch to S4. I guess that’s good news!

 

It’s not. I don’t want to touch the towing in S mode topic, but my owners manual says use S4 for engine braking, to provide engine braking and charging system performance. So slowing down, and S4 uses flex-lock to almost idle speed, so maximum engine braking. The biggest difference between tow/haul and normal or S mode is no flex-lock in tow/haul, it’s not good for towing and hauling. Lots of other changes also.

 

I’ll argue that the higher rpm shift points are still there. Form one stop sign to the next being in S4 with tow haul on or off you can watch and feel the difference. Not sure about any of the other changes that tow haul mode adds but I can see the higher rpm for each shift is there while in S4 and TH is on.

 

This is my experience as well.

 

Third that. There is a definite difference in shift points.

 

This is exactly what I do when pulling our Winnebago 2401RG. Found that there was an easy 35° temp difference between S4 and S5 on the flats with the same trailer (any headwind raised it by another 10° or so).

 

So 35 degrees higher in s5? Good to know

 

Yep, shocked the fool out of me. The temps weren't "bad" per-se, but were well over the 200° mark. I only use S5 now when I'm on flats and no wind at all, generally keep it in S4 as I get a solid 9MPG out of the truck when it's there.

 

Great thread y’all. Several tidbits I wouldn’t have expected

 

I was just about to haul an RV for the first time in mine and I stumbled across this thread. Great info that I will use.

 

Would you say 3,000 rpm sounds normal while driving 65 on a flat midwest highway in S4?

 

So what is the least amount of wear / tear on the engine and transmission when towing? From previous comments, it sounds like keeping the torque converter locked as much as possible is important. So S4 (or S5 on flat roads) with Tow/Haul mode? Sounds like T/H is actually enabled even though the FSM states it only works in D.

Just trying to summarize all the good points that I'm reading.

Thanks.

 

I agree with your assessment based on what I've read here.

 

Put it in D push the button and drive, just remember everything you read on the inter webs isn't true.

-Jason

 

The combo of “put it in D push the button and drive” along with “everything you read on the inter webs isn’t true” was quite the ironic pairing.

Can you just put it in D while towing? Sure you can!
Will this make your transmission temperature go to uncomfortable levels of 250F+ while going up hills? Probably, but you wouldn’t know unless you had a way to monitor the transmission temperature.
Myself and many other people on this forum have compared the transmission temperatures in D vs S4 and it makes a huge difference if you are dealing with hills. But we are all just part of the inter webs.

 

What you have to remember Aaron is the average "driver" these days, lives in a "Do It For Me" world. If their truck's transmission shifts itself to death while the Sequential Shifter sits unused, it's Toyota's fault!

 

I tow a 4500 lb camper. I tow in S5 with tow/haul engaged. I monitor the tranny temps with an Ultra Gauge. On hills, if I notice the tranny temp climbing, I down shift to S4 or even S3 (on steep hills). Works great for me and keeps me engaged...........

 

We may be twins!