I’ve been reading through this thread and just wanted to add my 2 cents.
I don’t know about Ford or Dodge, but GM doesn’t offer 4:10 gears in trucks equipped with the Duramax and hasn’t for a while near as I can tell. Apparently with the Duramax/Allison combination they don’t feel it’s necessary.
I just bought my 2500HD Silverado with the Duramax last November and have been using it as a daily driver ever since. Using winter blend fuel and letting it idle a few minutes 2-3 times a day to warm up I’m getting between 15-16 mpg combined city/hwy driving. With my old 2007, 1500 Silverado with the 5.3l I got 18.5 consistently doing the same driving I do now. So I’m losing 2.5-3.5 mpg with the diesel versus the 5.3l. As time goes by, I don’t think there will be that big of a difference.
The new truck has just over 2k miles so I expect as I accumulate more miles the MPG will increase and there should also be a difference once the winter blend fuel is gone. As far as the ride goes, the ¾ ton has a much stiffer ride that the old ½ ton... as it should. It’s a lot more truck. But, I notice the difference in ride more in town than I do on the highway.
Both of these…MPG and ride…are tradeoffs I was willing to make. I can’t say exactly what the difference in towing will be until this weather breaks and I can get to my camper. But I’m pretty sure the difference will be noticeable. The camper we have now is just under 6,000 lbs. loaded and the ½ pulled it ok, but to me it always seemed like the truck was maxed out once we got into any hills. I never felt like I had any cushion. I obviously don’t need a diesel to pull this camper, but the next one will be a lot bigger and I’d much rather have more truck than I need than not enough, or JUST enough.