mrgt350

What is the best f150 ecoboost gear ratio for mpg with 70/30 city-hwy driving?
3.31
3.55 or
3.73

borjeb

1 vote for 3.55. Coming from someone with 3.31s.

mrgt350

Borjeb,
Why do you say 3.55? Do you think the 3.31 lug to much in city driving?

BassAckwards

IDK the turbo kinda throws general rule of thumb out the window.

Because someone showed in another thread that the Engine was putting out like 9-10lbs of boost at low rpm take off. This would require a lot of fuel, so a lower rear end like the 3.73 might allow the engine to take off easier under normal engine power without producing so much boost.

Turbo's like tall gears to push against for performance and thats why the 3.55 actually has a better 0-60 than the 3.73.

The 3.73 may be better for City, but the taller gears would be better for Highway I'm sure.

borjeb

I think I suggest them cause I'd rather have them. Haha. I can't imagine the difference being more than 1mpg between all gears in city. But it leaves you some highway and some towing if you should need.

mrgt350

I drove a FX4 this weekend, 3.73. 75 MPH and rpm was 2000. 70 mph = 1800. From what I have gathered there is only 100 rpm difference between the 3.55 and the 3.73. So at 75 mph the 3.55 would be doing about 1900 rpms. Doesn't seem like alot and I am thinking the same on the city driving that it actually may be better with the 3.73.

reward69

Personally I would go 3.73, your still talking about a 6000+ lb truck. I dont think you will see enough mileage difference to out weigh the overall performance gains. If you plan on never towing or very low lb towing then I would go with the 3.55. To me your towing plans should make the decision. Either one I think you would be happy though.

BassAckwards

It's actually about a 250 rpm difference on my 06 with AOD, of course that can be different because of OD gearing mine being .7:1, the new six speeds have .69:1 and the Eco's Six speed has like .61:1

HankHill

It may be hard to tell. I have 3.31 on my 2000 xlt 5.4l. I can say it will light up the tires so it could benefit from more grip or even a taller gear. Now my ecoboost is heavier but has more power but I would also submit that if you do not tow much or at all, I would go with the 3.15 or 3.31 on a 2wd. If you ever plan on increasing tire size go with 3.55. On a 4x4 definatley 3.55 or 3.73. Because tire size may very well increase somwhere down the line plus towing power. I really believe there is enough power for either one to not strain or it would not be offered.

11screw50

actually, pretty sure they're the same.