SummitSitter

I’m going to be purchasing a 2018 F-150 XLT Crew Cab with either the 2.7 or 3.5 EB. I see there are choices of Rear Axle Ratios:

3.31 Electronic Locking Axle Ratio
3.31 Non-Limited Slip Axle Ratio
3.55 Electronic Locking Axle Ratio

What are the differences and what should I be looking for? I am not planning on doing any heavy trailering, and may want to do a front leveling and was told that a 305/55/20 size tire would be a good size to go with. Thanks for any assistance you can provide!

jstephens24tx

if your going bigger tires I think the consensus would be 3.55

SummitSitter

If I wasn’t going with bigger wheels, is there any advantage in one over the other? If I were to planning on towing, is the 3.55 the ratio you would want? Just trying to see what the differences are...

FirstKR

3.55 will always provide more power to the wheels than those other ratios at the expense of slightly poorer gas mileage.

So towing and bigger tires are both good reasons for 3.55

SteveLord

You want to be able to tow as much as you can out the door, even if you aren't towing anything now.

Stricnine

They don’t offer the 3.73? That would be my suggestion if you can get it.

JCR 56

3:55 , 3:73 if available.

Tom_with_a_Truck

I agree with others - 3.55 or 3.73 if possible. Bigger tire diameter benefits from the shorter (higher numerically) gear ratio. I thought that somewhere out there, there was a 4.10 gear option, but that might be very specific to certain models (the Raptor, perhaps). If you're going to go very large on tires, that would be a plus.

SummitSitter

Thanks guys. They do offer a 3.55 AND 3.73. I have about a 140 mile round trip commute to work, so I want to get the best fuel economy as possible. I know that going with bigger tires and a higher gear ratio will affect MPG’s. For argument sake, if Ford is saying you can get 19/24 MPG’s with the 2.7 EB...approximately how many MPG’s would you be dropping by going with a leveled truck with 305/55/20 tires and a 3.55 axle? Just want to see if it will drastically reduce MPG’s...

chimmike

3.31's on the 17+ 10sp are equivalent to 3.55s on the old 6 speed. or was it equivalent to 3.73's on the old 6sp?

somebody will chime in with the chart.