"Locking out 6th"?
Tuned
Joined: Jul 2003
Posts: 274
Likes: 20
It's simple really. When I hauling my 15K fifth wheel in constantly rolling steep Hill Country, I know that when it drops into sixth near the bottom of a hill it will be right back in fifth in a matter of seconds. If I lock out sixth I eliminate that quick shifting and everything is smoother and more consistent. If you don't tow heavy or encounter those kinds of terrain then you don't need to worry about it. But it is a great feature for those of us who do.
Laughing Gas
Joined: Sep 2017
Posts: 900
Likes: 330
If you're towing heavy, locking out 6th gear is a good idea, especially if in rolling hills. Sometimes you will need to lock out 5th as well. This works wonders and keeps the RPMs up so you don't loose too much speed uphill before it decides to downshift on it's own. When I was in the Blue Ridge mountains when I had my TT, I'd lock out 5th and 6th and was able to maintain speed up the hills without issue. A few times it went to 3rd, but kept pace with traffic nonetheless. It's also helpful going downhill as well.
Posting Guru
Joined: Jun 2018
Posts: 1,366
Likes: 186
From: Frederick, CO
The quick start guide you received with a new purchase has a good infographic for all of the features. The descriptions are a bit lacking and way too brief; the QSG doesn't really address the questions here. But, I grabbed the picture from the QSG to reference where the shift/gear selector is (8) and where the Tow/Haul mode button is (9).
Page 207 walks through the function of the Tow/Haul mode. This is also discussed frequently on these forums. You can learn a lot more by searching here.
Page 208 walks through the function of the "SelectShift" transmission feature and the "Progressive Range Selection (PRS)" feature. There is also a nice diagram showing the layout of the +, -, and Tow/Haul buttons on the gear shift lever.
I hope this helps provide the descriptions that have been summarized above (and elsewhere on these forums).
More Turbo
Joined: Mar 2018
Posts: 737
Likes: 13
It's simple really. When I hauling my 15K fifth wheel in constantly rolling steep Hill Country, I know that when it drops into sixth near the bottom of a hill it will be right back in fifth in a matter of seconds. If I lock out sixth I eliminates that quick shifting and everything is smoother and more consistent. If you don't tow heavy or encounter those kinds of terrain then you don't need to worry about it. But it is a great feature for those of us who do.
Tuned
Joined: Jul 2003
Posts: 274
Likes: 20
That's probably why I haven't used it yet. I see a lot of people talking about locking out the gears, but I've never noticed the need, because I don't ever notice it shifting around. However, I only tow 8200-8300 lbs, and the only hills I've encountered were some passes in PA on the turnpike on the way to Hershey, and some on I-75 on the way to Pigeon Forge, neither of which were more than a 3-4° by the scale on the gauge cluster. Anything steeper I've encountered have been on back country roads where I'm not rolling in the higher gears anyways.
More Turbo
Joined: Apr 2017
Posts: 736
Likes: 225
I lock out 6th if I am on hilly 2 lane road with 55 mpg speed limits while towing, That puts the 6.7 L engine in a better power band.
I also lock out 6th when on the interstate while towing if I know upcoming hills might cause my tranny to downshift to far to 4th trying to keep the cruise control happy. Downshifting to 5th prevents the surprise downshift to 4th.
I also lock out 6th when on the interstate while towing if I know upcoming hills might cause my tranny to downshift to far to 4th trying to keep the cruise control happy. Downshifting to 5th prevents the surprise downshift to 4th.
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Laughing Gas
Joined: Sep 2017
Posts: 900
Likes: 330
I lock out 6th if I am on hilly 2 lane road with 55 mpg speed limits while towing, That puts the 6.7 L engine in a better power band.
I also lock out 6th when on the interstate while towing if I know upcoming hills might cause my tranny to downshift to far to 4th trying to keep the cruise control happy. Downshifting to 5th prevents the surprise downshift to 4th.
I also lock out 6th when on the interstate while towing if I know upcoming hills might cause my tranny to downshift to far to 4th trying to keep the cruise control happy. Downshifting to 5th prevents the surprise downshift to 4th.
Tuned
Joined: Jul 2011
Posts: 396
Likes: 7
From: Wherever the RV is parked
I lock out 6th if I am on hilly 2 lane road with 55 mpg speed limits while towing, That puts the 6.7 L engine in a better power band.
I also lock out 6th when on the interstate while towing if I know upcoming hills might cause my tranny to downshift to far to 4th trying to keep the cruise control happy. Downshifting to 5th prevents the surprise downshift to 4th.
I also lock out 6th when on the interstate while towing if I know upcoming hills might cause my tranny to downshift to far to 4th trying to keep the cruise control happy. Downshifting to 5th prevents the surprise downshift to 4th.
Cargo Master
Joined: Feb 2005
Posts: 2,898
Likes: 185
Plus you get more engine braking with the upper gears locked out. Tow haul by itself isn't so great. I take it you have never towed before?
