3.55 Rear Axle?
#1
3.55 Rear Axle?
So I've seen a few posts about rear axles and ratio's etc but I don't see too much mention of the 3.55 ratio with the EcoBoost motor in the F150 4by. Yet when I configure a F150 SCrew 4by with Eco, it automatically defaults/adds the option for 3.55 LS ratio. Also, most if not all F150's I've seen on the lots around here with the Eco have the same 3.55. Is there something I'm missing here...why are most people posting that they have something different? I hope the 3.55 will be good, 'cause my truck is on the way from the factory with it in it.
#2
A lot of folks are special ordering their new F-150's with 3.73:1 gear ratio. It will improve towing and help for those that put larger tires on their trucks. The 3.55:1 setup is an average mid-range ratio good for highway driving and is probably considered standard equipment on a lot of models. Don't expect to get the best fuel mileage with a 3.73:1 but if you look at a lot of picture of some of these truck you would think there isn't much consideration except trying to make the truck look good.
#3
#4
These are the axle ratio's listed under, CONVENTIONAL TOWING - MAXIMUM LOADED TRAILER WEIGHT RATINGS (LBS)
3.5 Ecoboost
3.15
3.31
3.55
3.73
4.10
3.7 V6
3.55
3.73
5.0 V8
3.31
3.55
3.73
6.2 V8
3.73
4.10
I'm not sure if this means these are the only axle ratio's available for the respective engine or not.
#5
IMO, unless you will be towing >5,000 lbs much of the time or for long distances occasionally, the 3.55's will be just fine, even with 33's.
You have to keep in mind that the 6-speed has some very low gears (1: 4.17, 2: 2.34, 3: 1.52, 4: 1.14, 5: 0.87, 6: 0.69) and you have the ability to lock out O/D so you should be able to keep the engine at or near peak torque for most of your driving needs.
You have to keep in mind that the 6-speed has some very low gears (1: 4.17, 2: 2.34, 3: 1.52, 4: 1.14, 5: 0.87, 6: 0.69) and you have the ability to lock out O/D so you should be able to keep the engine at or near peak torque for most of your driving needs.
#6
#7
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#9
If you're driving down the road in your truck equipped with 3.31 gears, going, say about 65 and let's say that tach is reading 1600 rpm.
If you were driving with 3.55 gears, you'd be taching 1700 rpm.
With 3.73 gears you'd be taching 1800 rpm. It's a linear function.
4.10 gears would put you at 2000 rpm. Now we're taking some additional fuel burn.
It would be nice to test drive various geared vehicles and see what the difference is, but most of us don't have access to a bunch of test trucks.
My experience is that getting high speed gears, like 3.31s for better milage in a mountain environment can backfire, as the vehicle has to downshift sooner going uphill, whereas it might make the grade in a higher gear. The fuel burn on a downshift is very pronounced. The engine has to make the same HP to get up the grade at a constant vehicle speed, but is more fuel efficient at the lowest engine rpm.
Another point of interest is that some F-150 4x4 models with the 18 inches wheels which means 275x65x18 tires.
The optional 20 inches wheels come with tires that are 275x55x20.
What interesting is that both these tires sizes are virtually identical in diameter; 32 inches, for whatever that is worth.
If you were driving with 3.55 gears, you'd be taching 1700 rpm.
With 3.73 gears you'd be taching 1800 rpm. It's a linear function.
4.10 gears would put you at 2000 rpm. Now we're taking some additional fuel burn.
It would be nice to test drive various geared vehicles and see what the difference is, but most of us don't have access to a bunch of test trucks.
My experience is that getting high speed gears, like 3.31s for better milage in a mountain environment can backfire, as the vehicle has to downshift sooner going uphill, whereas it might make the grade in a higher gear. The fuel burn on a downshift is very pronounced. The engine has to make the same HP to get up the grade at a constant vehicle speed, but is more fuel efficient at the lowest engine rpm.
Another point of interest is that some F-150 4x4 models with the 18 inches wheels which means 275x65x18 tires.
The optional 20 inches wheels come with tires that are 275x55x20.
What interesting is that both these tires sizes are virtually identical in diameter; 32 inches, for whatever that is worth.
#10
[QUOTE=Truckpilot1329;10869997]If you're driving down the road in your truck equipped with 3.31 gears, going, say about 65 and let's say that tach is reading 1600 rpm.
If you were driving with 3.55 gears, you'd be taching 1700 rpm.
With 3.73 gears you'd be taching 1800 rpm. It's a linear function.
4.10 gears would put you at 2000 rpm. Now we're taking some additional fuel burn.
It would be nice to test drive various geared vehicles and see what the difference is, but most of us don't have access to a bunch of test trucks.
My experience is that getting high speed gears, like 3.31s for better milage in a mountain environment can backfire, as the vehicle has to downshift sooner going uphill, whereas it might make the grade in a higher gear. The fuel burn on a downshift is very pronounced. The engine has to make the same HP to get up the grade at a constant vehicle speed, but is more fuel efficient at the lowest engine rpm.
Another point of interest is that some F-150 4x4 models with the 18 inches wheels which means 275x65x18 tires.
The optional 20 inches wheels come with tires that are 275x55x20.
What interesting is that both these tires sizes are virtually identical in diameter; 32 inches, for whatever that is worth.[/QUOTE]
That's worth a lot as there are tons of tire related questions on here. Many folks don't realize that little tidbit about factory 18's and 20's.
For the ecoboost engine, I would consider the 3.55 axles to be optimal unless one is towing 11k every day.
If you were driving with 3.55 gears, you'd be taching 1700 rpm.
With 3.73 gears you'd be taching 1800 rpm. It's a linear function.
4.10 gears would put you at 2000 rpm. Now we're taking some additional fuel burn.
It would be nice to test drive various geared vehicles and see what the difference is, but most of us don't have access to a bunch of test trucks.
My experience is that getting high speed gears, like 3.31s for better milage in a mountain environment can backfire, as the vehicle has to downshift sooner going uphill, whereas it might make the grade in a higher gear. The fuel burn on a downshift is very pronounced. The engine has to make the same HP to get up the grade at a constant vehicle speed, but is more fuel efficient at the lowest engine rpm.
Another point of interest is that some F-150 4x4 models with the 18 inches wheels which means 275x65x18 tires.
The optional 20 inches wheels come with tires that are 275x55x20.
What interesting is that both these tires sizes are virtually identical in diameter; 32 inches, for whatever that is worth.[/QUOTE]
That's worth a lot as there are tons of tire related questions on here. Many folks don't realize that little tidbit about factory 18's and 20's.
For the ecoboost engine, I would consider the 3.55 axles to be optimal unless one is towing 11k every day.
#12
#13
With the 3.55, you'll be more than well equipped to handle most any task that an F-150 is rated for.
#14
But the good thing about the ecoboost engine with any gear set is that you can tow. I believe the 3.15 axle gets you a 7500 lb tow rating. That speaks volumes for the engine / transmission duo.
With the 3.55, you'll be more than well equipped to handle most any task that an F-150 is rated for.
With the 3.55, you'll be more than well equipped to handle most any task that an F-150 is rated for.