Tow haul or OD off

I'm looking for a little knowledge. My old truck just had one mode "tow haul" used while towing. My 2006 5.7 cad cab appears to have 2 modes. Push
the button once and it says it is in "tow haul" mode. Push it again and "tow haul" goes off but now "Over Drive Off" is displayed. I've read the owners manual and I'd say the wording is anything but direct.
So with Vacation coming soon I'm trying to gather knowledge. I'm pulling a 5500lb trailer and we are headed for the mountains. Do I use "tow haul" or "over drive off"? I understand "tow haul" alters the shift points? and "OD off" lock out OD? But I'm having trouble understanding when to pick which. And why do you not need both at the same time which does not appear to be an option, right? One or the other are my only displayed choices.
Can someone help me out?
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transmission shifts fine like this with my 7000 pound trailer.
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Dan Ward wrote:

trans works. Yow/Haul is also an O/D Off, but also the transmission shifts later, holding the truck in gear to get a little more towing power. Current transmissions shift very soon in an attempt to increase fuel mileage and decrease emissions.
--
.boB
Arrived: 2006 FXDI, Red.
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