pnichols wrote:
otrfun wrote:
Can I politely assume you haven't driven a Cummins with the cruise on, the exhaust brake (EB) set to auto, while driving up and down 5-7% grades with, say 13,000 lbs. behind you . . . with your feet relaxed on the floorboard? ... snip
I've never owned a diesel ... but I have driven our 12,000 lb. RV up and down 5-7% grades while leaving the cruise set on and yes, the transmission does automatically downshift to whatever gear is necessary to maintain whatever speed I have set the cruise at. If I'm not in cruise, then subsequent brake taps bring the gearing down to whatever I need or want on downgrades.
However as I mentioned earlier my rear differential is a 4:56, so that helps tremendously with hold-back from 5th gear on down.
I've driven a number of gas vehicles that auto-downshift for braking as you describe. If you were to personally drive those same grades with any of the late model Big 3 diesels (cruise on, auto EB activated) I believe you would better appreciate how different true engine braking is vs. simple downshifting.
