Tow Haul Is Stoopid!

I also have the OBD reader and Fusion app and can verify the same, the S mode is simply to limit the transmissions highest gear. That is S4 only allows 1st through 4th gear, preventing upshift to higher gears. S5 only allows 1st through 5th gears.

Around town and any ware I'm not traveling faster than 60 to 65 mph I keep my truck in S5 always, I've found this keeps the tranny from constantly shifting between 5th and 6th gears and helps prevent unnecessary heat and wear,

 

I tow in drive all the time with no issues at all. I'm not towing 8000 lbs, but shifting into overdrive is not going to hurt anything. The only issue you'll have is if you are constantly shifting in and out of it which will heat up your transmission. No reason to be scared if it shifts into overdrive. If it starts shifting constantly to hold speed, then downshift into 4.

 

I agree with you both. I was just pointing out what the Owners Manual states. The OM didn’t phrase it using the condition “if traveling on downhill grades use S4 to help with engine braking...”

I think it was stating it as “you should tow in S4, and oh by the way, it’s a smart thing because it helps with engine breaking considering the combined weight of the truck and trailer...”

 

This entire conversation seems to be based on the premise that you should not tow in overdrive. I don't know why that should be the rule. As long as the engine has enough torque to maintain speed and you are not overheating either the engine or transmission, I don't see the problem.

 

I am. Does anyone want to explain it to me? Google was unhelpful.

I was under the impression that the torque converter will only unlock while driving at highway speeds in 5th or 6th gear but it seems that's not the case based on the discussion in this thread?

 

Dumb question:

I’m not a seasoned hauler but when towing I’d much prefer to sacrifice a few MPG and keep the transmission cool.

Specifically if I’m towing MPG is garbage anyways so I’d just prefer to leave in S4 with piece in mind the transmission will be cooler and not hunting. And that’s not even bringing up the lack of trans coolers in the 2019+...

 

Tow Haul mode and S4 = easy towing at 65 MPH or less. I still cringe when I get passed by guys pulling a huge trailer at 75 down the interstate. So much easier to just leave 30 minutes early and cruise at 60.

 

Pulling a long hill in S4 I've had mine go in and out of lockup dependent on what the throttle valve angle is versus velocity.

 

Me too. Not to mention it's what Toyota recommends in the manual.

 

Yep!

I get passed constantly by big box RV's going 80mph with improperly hitched rigs. Seems most guys are clueless on how to set up a weight distribution system making it all the more dangerous!

BTW I spent ~3 hours and 6 or 7 different set ups of an Equal-i-zer WD hitch. I was close before, within specs but now the Tundra and Airstream Flying Cloud are both dead level. Rides like on rails even when windy and a semi blasting by.

BIG Equal-i-zr fan! HATE Blue Ox chain style hitches and happy to share my reasons if you're curious or trying to decide.

Greg