Duramax vs Power Stroke Fuel Economy Tow Test and Drag Race

4x4ord wrote:

ShinerBock wrote:

Cummins12V98 wrote:
"I think the 3.42 rear end on the GM might have had an effect on mpg here especially if they let the truck do all the shifting."

But But, I thought the magical 10 speed was supposed to keep the engine in the perfect rpm???

This is not due to it being a 10-speed but rather the trans tuning. Shifting manually or having a shorter final gear would alleviate this. To be fair, I had to do the same in my 68RFE when it had stock trans tuning and so do my friends and family who have Aisin's so Ram's stock trans tuning is not perfect either.

When do you manually shift a transmission with stock tuning? What are you trying to accomplish by manually shifting?

I should have reworded that bnecause you can't actually shift manually in a Ram like you can in a Ford which is one thing I missed when I went from my F150 to my 2500 because there certain situations where it was helpful like starting the truck in second gear in slippery conditions. You only have the ability to lock out gears in the Ram and in this case I would lock out 6th to keep the truck from going into second over drive.

Both 5th and 6th are overdrive gears on the 68RFE as it is with most 6 speed transmissions. With a 3.42 rear end and 34 inch tires, 6th gear puts me in a great rpm unloaded(1,500 @ 75 mph) and 5th puts me in in the prefect rpm loaded(1,800 @ 65 mph).