How come in oder to prevent a parked vehicle from rolling down a hill, always place the transmission in low gear for a manual transmission? Thank you!
If the emergency/hand/park brake was to fail on a hill, the vehicle would start to roll down the hill. If the manual transmission had a gear selected, the vehicle’s rotating road wheels would cause the engine to also rotate, this would at least slow the vehicle down.
If the highest gear was selected, one rotation of the road wheels would likely cause the engine to rotate once.
If a low gear is selected, one rotation of the road wheels would cause the engine to rotate several times, adding more friction/load than in a high gear.
What you would actually find in a low gear is that there would be so much friction added by the engine that the vehicle would not move at all even with the brake fully off.