Please guys. I have trouble keeping those speeds under 100. ESPECIALLY down hills.

For the quietest diesel I've known so far, I'd say the 350 is the best. You cannot even hear the engine at 80 mph. You CAN hear the BFGoodrich Advantage Plus treads making contact with the pavement.

Watch those speedometers folks.

BTW, the 617 seems quite peppy at 70 - 80 mph. After 90 - 95, they start to "die out".