One of the very few disappointments I have (21 3500 Laramie LWB H.O. Aisen) is with all the great gauges to monitor they didn't offer a pyrometer!?
Baffles me as to why they would forget if not the absolute most important gauge to monitor. Years past, this was what was used to shift. This would be very helpful and telling for the OP's question as to when to shift. You can monitor the instant mpg's along with rpm, but lugging can really be defined by exhaust gas temps. RPM isn't necessarily directly related to rpm. EGT's don't lie. A higher rpm can result in better fuel economy. Normally we want to get into the highest gear asap, while keeping egt's low=best mpg. Understanding the relationship between our engines torgue curve, rpm's, and speedo makes a huge difference. I have noticed with these newer Cummins engines(whether standard or H.O.) they build a ton of torque at low rpm. So it can be difficult to relalize when we are lugging. Our trannies computers do alot of this now(unlike the old days) so I would offer to the OP to pay attention to the trans downshifting then upshifting. If it's doing that, pull it down agear until it stays. Searc shifting back and forth equls heat. We do have both engine and trans temp gauges which is super helpful in our driving habits, but I wish Ram would have included a pyro along with the mix. If your lugging, that pryo will be high revealing wasteful unburn fuel, high temps, and underpowing/taxing drivetrain components. Hope this makes sense. Great question btw.
