I can tell you if it's the same 6 speed auto backing the expedition it makes a nice difference. I'm running a 6500 ( w/ me at 250 lbs in it) lb expedition (EL 4x4 w/ two dog boxes and trays etc) and a ton of work stuff and i'm getting 17 to 19 on the highway (19 under 65 mph) and it runs much better then the old 4 speeds. The 6 speed really makes a huge difference, 1st gears 4.17 to 1 ratio is huge and then add in 3.73s w/ a 2.7 to 1 low range, it's got a nice crawl ratio.