motrapper

been pulling alot with truck and shifting about 2500rpm was wondering should a guy wait till 2800 rpm or what is the best in all gears also we have half mile hills at some unreal grade in these hollers dont know if people down here spell it like that or not
but this is my first hand shaker and was wondering

thanks

GrandpasRam

2600 rpm should be a good upshift point; seems just right on mine with the 3.73 diff ratio and stock tires. If running empty, about 200 rpm less seems just about right. The ECM begins defueling at about 2700 or so rpm, and the torque and HP curve starts falling off at about 2700, so anything past that isn't going to buy you a lot.

Buckshotmckee

2500 seems fine. Every situation is different. I drive by feel myself.

bigblock2stroke

Peak power is at 2900rpm so hopefully you aren't defueling at 2700rpm.

You can shift wherever you want, the important thing is that when you let the clutch out in the next higher gear, make sure you are at or above the torque peak.

GrandpasRam

True; I forgot the newer ones were turned up by 200 RPM for both redline and defueling - you are correct. According to the Cummins website though, the HP and Torque curve start falling off between 2700 and 2800 RPM (small amount of fall-off until 2900 to 3000 where the defueling begins). Good catch bigblock.

The engine will usually let you know when it wants to be shifted; when new and breaking in it seems like around 2500 it just doesn't want much more, after some break-in miles towing, it seems to take a bit more before letting you know it wants to be shifted.

hllbllyhellion

I saw somewhere on the net where one of the new 600's were dyno'ed at the rear wheel don't remember tranny or ratio but peak torque was 2200 rpm and hp was 2800 rpm. if memory serves me correctly?

sherman

2200 rpm sounds high for peak torque for the Cummins,I think it's closer to 1600rpm. My 04 peaks at 1400rpm.