Original post by: Your ,
Loose the mindset that you "don't want to creep up hills going 30mph." Going uphill fast is the biggest loss of fuel economy you will encounter on the road. To answer the question: You will need to do as much research on all of your available options. However, I think the volvo I-shift can be in a direct drive configuration. The Volvo engines aren't great but still much better than the cummins. Here's how I would probably spec one. Volvo D13 engine Direct Drive I-shift 2.64 Rear end ratio (with direct drive trans only or 3.55 with OD trans., optimal around 62mph but not terrible at 65) Single drive axle with tag axle if available.