The Cummins soon to take on the Ike

blofgren wrote:
I'm guessing the Ram will run similar to or a bit slower than the Duramax. I'm sure the 6 speed transmission will be a factor in this, although the Cummins has a sweet, flat torque curve that should make this less of a disadvantage.

The Cummins has a flat power curve. The torque curve drops off faster as the rpm increases with the Cummins than the Duramax does and that's why it makes less hp than the Duramax even though it makes higher peak torque. The working rpm range of the Cummins is probably 2100 -3100 rpm? We know it makes 343 hp at 1800 rpm and 400 hp at 2800. It likely makes at least 376 hp at 2100 rpm, then 394 hp at 2500 rpm and 385 hp at 3100 rpm.
We can guess that the Ram will make most of the run in 3rd gear running above 2500 rpm which puts it at 43 mph. The last mile and half will probably bring it to its knees in third or it might drop to second. At any rate it should be spending very little time below 380 hp. So if the six speed keeps it between 380 and 400 hp there isn't a whole lot to be gained by more cogs in the transmission.