2015 Expy Final Gear Ratio upgrade - advise required

[Dion Rebello]

Hello All,

I have a 2015 Expedition XLT (4x4) with 295/70 R18's (34inch) tires, (OEM tires were 32inch)

Please can you let me know what is the current final gear ratio...and recommended upgrade (no towing)...and I do have to change final gearing for front and rear...correct?

Many thanks!

#bronz_fire

 

[shinysideup2]

You do have to have front and rear matching. What's your current ratio? What do you not like about it? What's your goal and intended future use of the Expedition?

I have the 3.73 (3L73 Limited Slip) which is very good for towing, acceleration, and over-sized tires (34").

 

[mjp2]

I went from 3.73 to 4.11 gears with 35" tires and the truck is WAY happier. The shift points are spot on even when towing.

If I didn't use the truck for long road trips I'd have gone with 4.56 gears to get more power to the ground and put less strain on the drivetrain but this ended up being a solid compromise. Engine's turning about 100 rpms higher at highway speed vs stock gears/tires.

 

[LokiWolf]

Like was asked by SSU2, what packages do you have on your Expy. If you have Heavy Tow, you have 3.73 and there is absolutely zero reason to change gearing with 34's. MJP2 experience is based on the 5.4. The 2015 has the Ecoboost and already makes more torque even lower. Leave the diffs alone.

 

[JasonH]

Hello All,

I have a 2015 Expedition XLT (4x4) with 295/70 R18's (34inch) tires, (OEM tires were 32inch)

Please can you let me know what is the current final gear ratio...and recommended upgrade (no towing)...and I do have to change final gearing for front and rear...correct?

Many thanks!

#bronz_fire

The sticker on the driver's door jamb has the axle code. The Ecoboost generates a lot of torque down low, no upgrade needed.

 

[Dion Rebello]

You do have to have front and rear matching. What's your current ratio? What do you not like about it? What's your goal and intended future use of the Expedition?

I have the 3.73 (3L73 Limited Slip) which is very good for towing, acceleration, and over-sized tires (34").

My fuel economy just dropped after changing tires, so want to get that improved. Highway speeds upwards of 75-80miles an hour and the truck feels lethargic...

 

[LokiWolf]

My fuel economy just dropped after changing tires, so want to get that improved. Highway speeds upwards of 75-80miles an hour and the truck feels lethargic...

We are still waiting. Do you have Heavy Tow? You could post the Axle code too. What brand tires did you add? Going to a bigger axle ratio will not gain you MPG. Based on the fact you put 34's on, I am guessing you also did a lift like the 3/2. Did you recalibrate the speedo/odometer for the difference in rolling diameter. Because any calculation you are doing is off.

So you lifted it(Increased Wind Resistence), added larger(most likely heavier) tires, and are surprised you had a decrease in MPG? Increasing the gearing is not going to help with that.

 

[Dion Rebello]

We are still waiting. Do you have Heavy Tow? You could post the Axle code too. What brand tires did you add? Going to a bigger axle ratio will not gain you MPG. Based on the fact you put 34's on, I am guessing you also did a lift like the 3/2. Did you recalibrate the speedo/odometer for the difference in rolling diameter. Because any calculation you are doing is off.

So you lifted it(Increased Wind Resistence), added larger(most likely heavier) tires, and are surprised you had a decrease in MPG? Increasing the gearing is not going to help with that.

Not sure about HD Tow package...how can I find this out? I knew my MPG wud suffer after the tire increase, but I was hoping with re-gearing I cud better this.

 

[bloodhound]

Not sure about HD Tow package...how can I find this out? I knew my MPG wud suffer after the tire increase, but I was hoping with re-gearing I cud better this.View attachment 71860

You have axle code 15 which is 3.31 gears.

 

[Dion Rebello]

We are still waiting. Do you have Heavy Tow? You could post the Axle code too. What brand tires did you add? Going to a bigger axle ratio will not gain you MPG. Based on the fact you put 34's on, I am guessing you also did a lift like the 3/2. Did you recalibrate the speedo/odometer for the difference in rolling diameter. Because any calculation you are doing is off.

So you lifted it(Increased Wind Resistence), added larger(most likely heavier) tires, and are surprised you had a decrease in MPG? Increasing the gearing is not going to help with that.

Not sure about HD Tow package...how can I find this out? I knew my MPG wud suffer after the tire increase, but I was hoping with re-gearing I cud View attachment 71860

You have axle code 15 which is 3.31 gears.

Thank you!!! Can you let me know how you found this out? and just being sure...I'm assuming this is front and rear?
Also, if I am to go by the general formula - (New Tire size x OEM Ratio) / Old tire Size - I get 3.51 new gear ratio...