DT12 vs 13 speed

Another option is to tap the acc button when it goes into "e-coast", it'll promptly go back into the gear it was in.

 

I currently drive for Frito Lay and all of our trucks are single axle Volvo's with the I-shift transmissions and I would strongly encourage you to go with the 13 speed over an auto-shift. My current truck has issues in every aspect of shifting. It will start off in 1st gear skip to 3rd, then 4th tach up to 2200 rpms through 5th & 6th, shift to 7th for a second then shift to 8th and tach up to 2200 rpms again. It will also for a lack of a better phrase forget what gear it's in while upshifting, for example it'll shift into 5th on the dashboard but a few seconds later slam into the gear and shock the drivetrain then it will do the same for the next two gears. Also, the transmission will upshift to such a high gear that the entire truck will shutter and the raise rpms icon will come up on the dashboard. I have had the transmission computer flashed to relearn how to shift with not change. When it comes the braking unless you manually downshift the transmissions it will simply throw it's into neutral and rely souly on the brakes to stop the truck even with the Jake brake on level three. Fuel economy is a joke when it comes to auto-shifts, my current truck has the D13 Volvo engine with the 12 speed I-shift and averages 7.4 mpg, if I drive the truck in manual mode I can get 7.5 mpg @ 65 mph. While my truck was in the shop and I was in a rental truck (Freightliner) with a DD13, 10 speed transmission, 3:55 gears and tandem axle I was getting 7.8 mpg @ 65 mph.

 

I was messing around with mine in California last trip. Since the speed limit is 55 I set it up in Manual mode and 11th gear. Came in on I-40 and up CA-58 to CA-99 and over to San Fran. 11.1 miles per gallon. Got re-loaded and back to Kingman AZ for my 10 hour break the computer was showing 8.1 mpgs.

So much nicer to keep it in Manual mode to prevent that stupid Ecoast. Manual in 12th gear was about 1000 rpm which seemed to lug the truck too much. Will have to try it next trip in.