pnichols wrote:
otrfun wrote:
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.
Hmmm .... I'm tempted to say that "downhill holdback" is "downhill holdback" .... with respect to diesel exhaust braking versus gas gear braking whenever a given weight vehicle combination is able to be slowed enough or too much.
However, since the exhaust braking engine back pressure mechanism is different than the gear braking engine back pressure mechanism ... maybe exhaust braking can somehow feel different to the driver. :h
Hmmm, I'm tempted to say you have no idea what you're talking about....
