Thanks everyone for the great replies.
I finally tweaked our W.D.H. and towed up to the local Truck Stop and weighed it on CAT Scales.
Truck is 2017 Colorado Crew cab Diesel short bed. It has factory towing package with tow haul mode and the integrated trailer brake control and with exhaust brake.
It's set up just like our 6.6 Crew Cab dually's were, just not all the beef. LOL
Truck Max ratings as follows: GVCW 12,700 lbs. Max trailer weight towing 7,700 lbs. Max hitch/tongue weight of 760 with W.D.H.
Trailer loaded and Truck weights on Scale: GVCW 11,460 lbs. Trailer loaded weight 6,000 lbs. Tongue Weight 640 lbs.
We're 1,240 lbs under Max GVCW rating. Trailer loaded is 995 lbs under Max GVW rating. Tongue weight is 120 lbs under Max Rating.
All axles are under G.W.R .
Truck is under it's Gross Vehicle Rating.
Tows easy and like a dream compared to the Coleman 1705 RB. as far as ride and sway.
Plenty of power cruising at speed limits and getting out in traffic, don't know where this little diesel gets all of it's pulling prowess.
We had towed the Coleman briefly with a 2016 Silverado High Country Crew Cab 4x4 5.3 with 8 speed tranny.
It was always shifting down and revving up on any grade, even slight ones.
Not saying it didn't have enough power but was always searching for a gear whether in tow haul or not.
Got 10 mpg towing.
We were getting 15 towing the Coleman with the Colorado at 55 mph and 14 at 65 and 70 mph.
I like to stay at 65 mph uses less fuel and a lot safer.
Going the 20 miles to the Scale and back with the 22MLE I was getting 14.7 running 55 mph and briefly 45 mph in a couple of speed limit areas.
Have a trip planed for Sunday about 90 miles to campground. I'll know better what real world mpg numbers will be by then.
I suspect we will lose a couple of mpg towing the extra 1,000 lbs, but the drag is about the same. The Coleman was shorter but same width and height.
That parachute that we pull with a tall wide trailer. LOL.
Anyways I'll let y'all know how it goes then.
Thanks again for all of the input.