I got the chance to drive a 2016 Kenworth T680 with the MX-13 Paccar motor in it with a 10 speed Eaton autoshift behind it. While I was not impressed with the transmission, the motor is very nice. Truck was showing 8.5 mpg average on my linehaul run of 650 miles a day from Cheyenne, WY to Kearney, NE and back every day I ran it. Pulled very well, has so much low end power it broke traction violently when I stomped on it accelerating back onto the interstate on a wet road. One of my co-workers was right up my rear trailer bumper one day until I fed it the fuel. I was pulling slightly heavier trailers and his Freightliner might as well have said powered by Briggs & Stratton at that point. I ran off and left him, and made the gap bigger every hill we pulled. This transmission is slow to complete shifts and horrible to get to feather. Backing up with it makes you look like you been driving for 5 minuets. Creature comforts are the best in this truck. Chair is great, suspension is set up where it just glides down the road. You only feel the big bumps. These trucks all have 500,000 miles on them currently and are the best running and driving trucks in the fleet.
The current one I run is a 2019 International LT with the ISX 15 Cummins and Eaton endurant 12 speed autoshift. This one won't pull quite as hard as the Paccar MX-13 but it's close. It shows fuel mileage average of 7.9 mpg on the same run as the Kenworth. Engine is very quiet and smooth. The endurant is a very nice transmisson for an autoshift. Smooth, very quiet, no gear guessing games, no missed shifts and no accelerator pedal use required to make it start to move. Just take foot off brake pedal and it very gently eases out on it's clutch and goes. It gave me a pleasant surprise one day when I was still a city delivery driver in some gooey mud: I forgot to hit the button to lock it into a gear and it didn't try to upshift until well after it got clear of the mud. This is the only autoshift I have driven that doesn't make me miss a manual transmission. This truck also has good creature comforts. Ride is nice, though not as nice as the Kenworth. So far only 100,000 to 200,000 miles on these trucks. Issue drivers have with these is the trailers being loaded too nose-heavy for them so the drive axle has over-weight problems. The company is making adjustments for this on the docks when loading. Moving the 5th wheel hitch forward will lead to the trailers kissing the cab on turns. The cab on these is set further back than the Freightliners or Kenworths.
Most of my companies fleet is Freightliner Cascadia's with the Detroit Diesel DD13 and their in-house 12 speed. The engine pulls and performs ok and is reliable. I have not been impressed with this transmission though. It loves to try to skip too many gears sometimes, lugs then skips back down and keeps this up instead of just hitting the gear it keeps jumping over. I have had several of these stick in a gear which was fortunately easy to cure by pulling over and shutting the truck down. Had a few that love to just miss a shift right in the middle of an intersection too. It also doesn't feather take-offs the best. I have slammed a few docks unintentionally because it thinks it has to dump the clutch randomly, usually about 2 feet from the dock. Creature comforts are ok on these. Chairs are usually good, but the truck rides rougher than the Kenworth or International. They rattle and get a lot more cab noise as a result. This isn't just the older trucks with 750,000 miles on them, but new ones as well.
These trucks are all 4x2 configuration used in a less-than-truckload operation, class 7-8. Figured I would share some observations since I get to drive and use new ones. It will be interesting to see how the engine market share changes.