S vs D and Tow/Haul Switch

Hi Folks. I will be picking up a 20’ travel trailer weighing in around 3800 lb dry (and later up to 4200 lb loaded) on Tuesday. Been a while since I have towed. I have a new Tundra SR5 TRD 4x4 with tow package and Max Trailer Weight Rating of 9600 lb. So trailer will be less than 50% of towing capacity (but could be greater if grey and black tanks were full before dumping). My question then, given the relative low weight of the trailer should I still use S mode and 4th gear on the AT (instead of D mode) and should I still engage the Tow/Haul switch? Thanks, Stephen

 

I would always engage tow/haul when towing. I would leave in D on flat terrain and use S mode to get out of OD gears on hills as necessary. Small hills get S5 and big ones S4.

 

Thanks, valuable info. The “leave in D” comment triggered a follow on question. If using D and on relatively flat terrain and driving around 60 mph, can I use cruise control?

 

I do without hesitation but only on flat terrain. I usually set mine around 65 mph and am pulling approx 6,000 lbs.

 

here are the pages. It says never use CC when towing and to always keep in S4 to maintain emerging braking and charging efficiency. Also an explanation of T/H mode.it also says never use the engine in D mode when towing.

 

I have the benefit of an OBD trans temp monitor so I go ahead and save a few gallons of fuel by using higher gears when appropriate. Shifting in and out of 4-5-6 or using reverse up an incline is what gets these transmissions hot. I can run 6th gear towing at 70 mph on flat terrain all day and the trans will stay 195.

IMO the manual is a one size fits all rulebook that you can safely modify the rules to if you know what you’re doing and what to avoid. The manual has to assume you’re towing maximum weight and will tell you to take precautions as though you’re pulling max weight. I will occasionally put my truck in cruise control while towing because I know what lugging the engine is and how to avoid it even while using cruise. Drivers who don’t know or don’t pay attention can damage their truck.

 

I agree and since we don’t know the skill level of OP I’m giving him the specification ms for his truck as a baseline and then he can decide his own comfort level as opposed to bringing him up to our comfort level without the baseline. Now he also knows the reasons why Toyota recommends this. Ie.. engine braking disabled when in CC.

 

Looks like he just got the truck, he may not be as comfy modifying the rules as we are.

 

OP make sure you finish your break in period before towing as well.

 

I tow a 4500lb camper (loaded). I use Tow/haul and put the transmission in S5. I use an OMD transmission monitor. If I encounter a hill and see the transmission temp climbing, I down shift to S4 and the temp will drop. If it is a steep or long hill, I may have to shift to S4 or S3. Once over the hill, I shift back to S5. I rarely if ever use D or S6 when towing.

 

Thanks for the info. I had owned Tundra in past but did not tow with it. Anyway, yes, since picking up Tundra last Friday I drove 530 miles over 4 days and then 110 miles to fetch the Bambi 20’ today. I used Tow/Hall driving back home, mostly in S4, but some S5. Since the hwy from Greensboro to southeast of Raleigh, NC is flat to gently rolling I did use CC on occasion to bring my leg up to rest an acheing right knee. I tended to stay at 60mph, but on occcasion drifetd up to 65 mph. All felt ok and my crude dash temperature gauge for engine was normal. I don’t have a reading for the transmission.

 

Nice man! That first haul is intimidating! Sounds like your on you way to being a pro! Next big one is learning how to reverse!

 

Learned to reverse years ago, then forgot again. Stopped by parking lot of closed school on the way home from dealer. But could not yet get the swing of it. I know to start by turn truck steering oposite direction, but seems I start to jack-knife and cannot see association of corner of truck bed to trailer. So when I came home instead of backing into driveway I parked on street. My driveway starts going up and it could be that the 7 foot trailer overhang behind axle would cause trailer to bottom out on back end. I need to get my adult son to go with me to a parking lot and proctor me. Thanks for advice.

 

So think of it like this, you turn the opposite way until you get the pitch you want, then you correct immediately to the point that holds that pitch. You when you steer the trailer will continue to sharpen the angle until you correct. Try not turning so hard initially. You basically have to correct until you reach an equilibrium that will hold the angle you want. So turn opposite until the trailer pitches to the angle you want then start correcting until the pitch stops increasing. It’s not like reversing in a car where once you get the angle you want you just hold it there and the car will hold that angle. A trailer takes one steering wheel position to achieve a pitch, and then a lesser steering wheel position to hold that pitch you achieved. Tongue pull trailers are a bit squirrelly because they are sensitive. Especially short ones like yours.

 

Slightly different topic from the OP but would you guys also use S4 or S5 and tow/ haul when towing something very light? I was just trying to think about how I might tow my dad's boat if I ever end up offering to do that for him. It probably weighs 1500 lbs or less fully loaded and it's relatively flat between here and our lake lot.

 

@AZBoatHauler may have the info, I mean that’s literally his name but as far as me Inwould think you wouldn’t want to let it go into 6th gear at all when hauling. As far as T/H mode I think try it both ways and if you don’t feel you need the extra power or extended shift intervals then leave it off.

 

IMO It really depends on the actual weight being placed on the truck and how much you’re pulling. If the boat on the trailer ready to go truly is only 1,500 lbs, even 15% tongue weight only puts 225 lbs of weight on the truck which is a fair bit less than if I was sitting in your Tundra.

With these trucks weighing nearly 6,000 lbs, another 1,500 rolling behind it will be hard to feel if your hitch is at the proper level.

Long story short, I really don’t think it matters what you choose to do when you’re pulling something that light. The truck won’t know it’s back there.

All that being said, same rules apply whether towing or not, if you hit mountain grades or experience excessive shifting or gear hunting, put it in S mode and take over control. When I’m between two gears I always pick the lower one and let the revs go up. You’ll burn a little more fuel but it will be a much more pleasant drive and you’ll save your brakes if you’re going downhill.

 

I see what your saying. When would you not want to maintain engine braking efficiency or charging system performance? Engine brake is always on except for in cruise right? I haven’t read the section on engine braking but I thought that was the case. I guess I assumed that would be what would be preferable.

 

I agree with you. I guess I misunderstood what it was saying.

 

I look forward to my first tow with our Tundra. I'll be towing the same load I towed with our Sienna for 10y, so I should be in for a treat.

 

I use whatever gear the truck is happy to sit in and maintains trans temp. Without an external gauge that's hard to judge, but if you have an OBD2 reader or something else use that for reference. I routinely am in 6th gear even with heavy loads (6000lbs+), granted that's with a supercharger, but same logic applies to the trans regardless. 6th gear with the torque converter locked up and cruise controlled at whatever speed I want and trans will be at 190F and the truck is happy. I've seen people claim that the higher trans gears will get destroyed towing in a higher gear, I have yet to see any physical proof or logical argument to believe that's true.

Listen and watch the truck and do what makes it happy and you'll be fine.

 

I’m betting the difference will be huge! If you can dodge a wrench you can dodge a ball!! Or more specifically if you can tow with a van you can tow with a truck! Those siennas are nice man. So many creature comforts!

 

So no need for engine braking and or charging efficiency as your RPMs are already high. I’m with you and completely agree.

 

Yeah, I'm thinking I should pick myself up some kind of scan gauge and learn how to use it.

 

I use D and tow/haul towing 5000 lb boat. Relatively flat around here. With a strong headwind or hills i will use 5th. I only use cruise in known speed trap areas. Mainly one town and flat terrain at 50 mph.

 

My 2017 SR5+ has no tow/haul switch...but it appears to have the wiring for one under the antiskid panel. Any idea if I add a switch, will it give me the tow/haul functions?
I'm also adding a Tekonsha brake controller, so I'm thinking both will help my towing ability?