Bill,
Ford also has a "Tow/Haul" mode rather than an OD Lockout on some models (at least the current superduty trucks). Looking at my truck's service manual, it does the following:
- Uses all gears (including O/D)
- Changes the shift points so that they occur at a higher speed for a given accelerator pedal position
- Torque converter will lock up at lower speeds with a given accelerator pedal position
- Upshifts are temporarily delayed while decreasing accelerator pedal position during hill cresting to reduce excessive transmission shifting and to prepare for engine braking
- "Engine braking is provided in all forward gears without the requirement of moving the selector level"
- Manual "1", "2", and "3" selection is still available
- Grade braking downshifts happen when "positive vehicle acceleration is sensed", a "near zero" accelerator pedal position is obtained, and a minimum amount of time has expired since the last grade braking downshift". It's deactivated when you press the accelerator more than the threshold.
If I remember my Chevy right, it was similar. It turned on engine braking, made the torque converter lock up sooner, and changed the shift points. It also caused you to get 5 (or was it 7?) turn signal "winks" instead of 3 "winks" when you just quickly tapped the turn single indicator and increased the voltage of the charging system (presumably to better charge a trailer battery). It also used a different "learning memory" in the transmission than the normal mode (the transmission apparently learns when to shift over time - and that information is obviously different when towing than not). That was on a 2007.5 2500HD diesel. O/D was still used in tow haul mode.
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