Hello folks. I was just looking up this Tow/Haul info in our Owners Manual. Here is some good info:
"Use of ERS (or TOW/HAUL mode) also enables an
additional underdrive gear which is not normally used
during through-gear accelerations. This additional gear
can improve vehicle performance and cooling capability
when towing a trailer on certain grades. In ERS mode,
gears 1 though 3 are underdrive gears, and ERS 4 is direct
drive. ERS 5 and 6 (Overdrive gears) are the same as the
normal fourth and fifth gears.
NOTE: TOW/HAUL mode locks out Overdrive."
So, even though we have a 6 speed tranny we are only using 5 gears, 3rd is not used when in drive. 3rd is only used in Tow/Haul mode (but then you lose 5th and 6th gears) or if you manually put it in 3rd. But then you lose 4th, 5th and 6th gears. Thought it was really interesting that we have an unused gear the would help move this truck at lower speeds. Just thought I'd share that with you all.
That 'NOTE' you copied is for the 4 speed auto trans behind the 3.7l engine (see page 387 of the 2012 owners manual), not the 6 speed.
What does prevent it is :
Overdrive Operation
The automatic transmission includes an electronically controlled Overdrive (fifth and sixth gears). The transmission will automatically shift into the Overdrive gear if
the following conditions are present:
• the shift lever is in the DRIVE position,
• the transmission fluid has reached an adequate temperature,
• the engine coolant (antifreeze) has reached an adequate
temperature,
• vehicle speed is sufficiently high, and
• the TOW/HAUL switch has not been activated.
So the effect is the same, but the cut & pasted sections of the owners manual are for different transmissions