See also:

Parking on Hills
WARNING Parking the vehicle on a hill with the trailer attached can be dangerous. If something goes wrong, the rig could start to move. People can be injured, and both the vehicle and the trailer ca ...

Recommended Fluids and Lubricants
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Range Selection Mode (Allison® Transmission or Hydra-Matic® 6-Speed Transmission)
The vehicle may have a Range Selection Mode. The Range Selection Mode helps control the vehicle's transmission and vehicle speed while driving down hill or towing a trailer by letting you select a d ...