grampus

I appreciate all the comments about tow/haul mode. I'm well aware of it. I know how to use it and what its effects are. I've been using it for 12 years, with my old 2009 silverado and this 2020. That's not the problem. Nor is using cruise control. If I'm going up and down hills, I never use it. Nor do I when towing my heavier boat. This behavior came on suddenly during my last trip. Two hours into the trip, all on flat level roadways (other than bridges over rivers etc). A drastic change from how the truck has towed previously. Reread my op. My intention is to find out what changed suddenly. I have no intention of masking or bandaiding the problem. It the dealer can't fix it and tell me what's going on, my truck will be traded in for something else.

Interesting. I hadn't heard/read that. Makes one ponder. thank you adamace1

Wrong. It's a new truck that isn't operating as it is supposed to.

Maybe so, but it didn't behave this way before. I pulled my travel trailer to Atlanta and back from Detroit three weeks earlier, lots of flat road and lots of mountainous, with no issues. At 65mph on flat road and no head wind it looks like my second photo. Something changed during our last trip. Sometimes I use tow/haul mode, sometimes not. If it's flat and level with no head wind I typically won't use it. Towing my boat, I always use it.

This is a recent occurrence for my 1 yr old truck with 8500 miles on it. When towing our 3900# travel trailer, on flat level road going 60-65mph set on cruise, the engine varies between about 1800rpm/15mpg and 2700rpm/5mpg. It will hold at one end or the other for maybe 30-45 seconds then go back the other way. It does this continuously. Net result is a huge drop in fuel consumption and an angry owner. Prior to this trip, I had no issues, even when driving up and down the Appalachians with my travel trailer, or when towing my 5000# boat. When driving around town with nothing in tow, everything is fine. I took it into the dealer, but since no codes show up, they shrug their shoulders. From what I've been able to ascertain reading online, it seems most likely a torque converter issue? Does this sound right? I've posted two screen shots of a video I shot of the instrument cluster showing the extremes of behavior