Quote:
Originally Posted by number9
We have a '96 FLD120 flattop, 60Series Detroit 430/470hp, 10-sp Eaton & 4.11's pulling flatbed. Driver says he likes to run around 70mph and it turns 1,700rpm at that speed. I was worried about the mpg and had planned to trade out the gears for 3.55 or 3.70. A month ago we had it in the shop getting an A/C dryer and charged up and got an ECM printout and it showed Avg fuel useage of 6.9mpg :shock: After seeing that, I think I will leave well enough alone. Someday when one of the gears fail, I may swap out to a 3.70....maybe.
When I worked for Stevens, I drove a T2000 with a 435hp Cummins N14 direct 10 speed and 2.85 rear end and 22.5 lopro's. It was governed at 68 mph but would have turned at roughly the same RPM as your truck at 70 mph. With grossing between 70k and 80k on the average, I always averaged over the company minimum of 6.2 mpg, usually 6.5 or better.