Hello lanefj40
If you have your owners manual read it, it will help for your spefic vehicle. Loading your vehicle with weight, and driving w/o tow haul mode engaged, you will find the motor will shift sooner and rpm's will be lower than with tow haul engaged. Basically you are letting the vehicle know it's got work to do, and is not a soccer mom car right now. As mentioned above speed control using the motor on descents is also engaged with tow haul mode. Hope this helps.
Russ