Question Advice On Travel Trailer Towing

[buckspear]

I have a 2008 Tundra 4x4 DC SR5 TRD towing a 8500lb Jayco 32RLS Travel Trailer. There are a few issues I can't seem to find the answers for from my dealer regarding trailer towing:
1. When towing the trailer in tow mode - All other pickups I've owned the truck will not shift into overdrive when driving in the tow mode. With the Tundra it seems it will shift into 6th (high) gear regardless of what mode I'm in - is this normal? This may be fine in a perfect world but I find the xmission will hunt between 5th & 6th (on cruise control) unless you get your speed exactly right. Would it be best if I towed the trailer using the sequential shift mode only shifting into 6th when the conditions were right. This would also allow me to down-shift on hills to try and keep the RPM at the max torque of 3600rpm?
2. The operators manual mentions trailers can be towed without using the tow mode which can improve fuel mileage. However, the manual is quite vague explaining the proper conditions under which this should be done. Considering the weight of my trailer, I have tried going out of the tow mode only when up to speed on the highway and have found a marginal increase in the fuel mileage as they claim.
Any of you more experienced Tundra hands out there have any advice you could send me.

[Redram99]

I find the tow haul mode annoying when towing as it seems to hold lower gears to long(sticks in 4th way too much). Personally I use the seq shift option and only allow the tranny to shift up to 5th unless coming down a slight grade(then I let it use 6th). Then I can also use the engines compression braking ability on steep inclines and before corners.

For climbing hills, the trans will find the right gear and hold it... typically, but there are exceptions to every situation.
Also, I don't use cruise when pulling a trailer. I find it very hard on fuel when I do. You can do a much better job at fuel management by using your right foot. You can also keep the tranny from hunting on hills by using the pedal. I find that with cruise control if you are entering a slight grade the CC allows the speed to drop too much before applying throttle which causes the tranny to shift from 5th to 3rd and will hold 3rd all the way up the incline whereas by using my foot I can anticipate the grade and keep the tranny in 4th and maintain speed.
Just my 0.02

[roadstarca]

I have a large trailer also. I've towed it about 6-7,000 kilometers. I like using the sequential shift and leaving it in 4th gear. It doesn't shift and look for gears much once you are up to speed and you always have high RPM's and power on hand.

It didn't seem to affect fuel economy much. Loss in fuel economy verses tow/haul and letting the truck do what it liked was negligable. In 4th gear, I get 7-8 MPG at 65-70MPH.

This thread might get moved to the towing section.

[TundraBay]

See my other thread on a big tow Tundra as Tow-Mobile: 1,200 miles, 12,000 lbs, 10 MPG.

Finally, I did use the cruise control because otherwise without good foot control I kept speeding up to 70-75 MPH and watched my mileage drop. Used Tow/Haul mode which delayed upshifting and encouraged earlier downshifting (I think). I kept it about 60 most of the time. I used 91 Octane, mostly to stay away from Ethanol (yuck).

10 MPG wasn't bad for this big a$$ trailer.

[the_greenhorn]

you will just have to kind of find out for yourself - its all about driving style and what you're comfortable with. Tow/Haul mode is useful if you are towing a heavy trailer (which you are) in lots of steep grade hills because it will keep you in a lower gear for longer, which keeps the rpms up, which translates to more power while climbing - but also more rpm's translates to lower fuel economy. MPG is all about the rpm's.

If however, the path you take has little incline and is relatively flat - then there is really no need for tow/haul mode and you can keep it off. It is only a single button click away to turn it on or turn it off - so don't think that once you turn it on it HAS to be on the entire trip or vice versa.

As for sequential shift, I wrote in another post some time ago that I think it is just a little better than standard "D" mode. I was able to discern a difference on slight hills (and i do mean slight hills) that in sequential shift mode the truck was able to "stay in 6th" just a little bit better than when in "D" mode. How much of a difference in MPG? no way of knowing for sure, but my guess is almost NEGLIBLE. It was really just the piece of mind that on a small hill I could stay in gear and not have the truck pop down into 5th or 4th gear.

But like others have stated before - if you are towing 8500lb trailer, anything more than a moderate hill and your tranny will be trying to shift down into 3rd gear to maintain speed no matter what method you are using (sequential shift, "drive", cruise control on or off) and the only sure fire way to control that is with your own foot. If you get tired of using your foot - then set your cruise control and just get used to the fact that your rpm's and tranny will be winding up while climbing hills.

Once you drive 500-1000 miles with your truck - you'll figure out what works best for you.