Why do you Cummins guys want more gears
I’ve heard a number of Cummins fans saying they are waiting for an 8 or 10 speed transmission before getting a new truck. Why? Does the Cummins struggle to get your trailer moving from a stop? Or are ...
Forum Discussion
Devo the dog wrote:4x4ord wrote:
The ideal rpm range for the Cummins to be at towing a typical 15k fiver down a flat section of highway at 65 mph is between 1500 and 1700 rpm. I think 3:31 gears would work excellent.
Why at a lower RPM instead of at the peak torque?
The 2021 Cummins makes 1075 lbft of torque @1800 rpm. If you were going to work it at 70% engine load it would be very efficient at 1800 rpm. At 70% engine load it would be making about 260 hp. It would also be burning about 12 gallons of fuel per hour. If you were towing at 65 mph while burning 12 gallons per hour you’d be getting 5.3 mpg. Even at 50% engine load it might be quite efficient but even 50% load at 65 mph works out to 7.5 mpg. I’m guessing the Cummins would get more like 10 mpg towing a typical 15 k rv down the highway at 65 mph. Under light load conditions like that it will get a little better fuel economy at lower rpm as well as provide a nicer quieter towing experience.
