Possibility of going to a 3.73 on a 2013

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Dr0idattack

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I have a 2013 Expedition Limited 4x4 with Tow Package and I believe it has the 3.31 rearend. Is it possible or worth trying to find and swap to a 3.73 if I frequently tow a 28 foot travel trailer?
 

Adieu

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Look at your door sticker it has an axle code.

Same one that lists tire sizes pressures weights and seating
 

NASCAR Mike

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I thought about upgrading my wife's 08 Expy, RWD and no tow package from the 3.31 to 3.73. You need to swap the rear gears and get a tuner to update the rear ration in the computer so the speedometer is correct.

After I figured it would cost over $1,000 I decided against it.
 

chuck s

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If it's 4x4 you need two (2) axles of course.

Not a direct comparison but my 3.31 axles 2017 Expedition tows my travel trailer as good and probably better than my 3.73 LS 2007 model. Cruises on the interstate well below 2000 rpm. Probably 2200-2400 with the earlier truck -- no surprise comparing the ratios. Once you get a trailer moving the primary towing issue is air resistance and that ain't gonna change with an axle ratio. Acceleration maybe but we're not getting drag strip time slips. :)

-- Chuck
 

montecarlo31

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If you were really looking and savvy you would look for a '15 plus Lincoln Navigator that's been wrecked and grab the entire 3rd member. You can find them from the factory with 4.10s. That will make a night and day difference.

When I owned my expedition I had a loaner that was 2wd with 3.31s and I could tell quite a difference between the 3.31s and 3.73s. The 3.31 was very doggy and even when rolling lacked the oomph to keep it locked in 6th on even the slightest hills where as my 4wd 3.73 would pull the same hill in 6th.
 

1955moose

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If it was 2 wheel drive I say yeah, but 4 wheel like Chuck s said you'll need both differentials, and that gets expensive, unless you get a killer deal somewhere. Bottom line, live with what you got, trade up later to a newer vehicle that has the gearing you want. Messing with gearing can open a whole new can of worms, especially if you or a shop tried to swap out your differentials gears. If they dont shim/ tighten crush sleeves proper torque, it can be short lived.

Sent from my N9131 using Tapatalk
 

chuck s

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The 3.31 axle truck running in 5th gear is roughly the same as the 3.73 truck running in (fictional) 5.5th gear. So, yeah, the 3.31 truck has dropped down a gear but not as far down (increased rpm) as the 3.73 truck does when it goes to 5th. Not that any of this makes much difference especially since I suspect none of us tow more than occasionally. :)

-- Chuck
 

Boostedbus

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When I changed my old 95 F150’s gears from 3.54 to 4.10 it turned into a beast for towing compared to before. But that’s mainly because the 351 doesn’t make great low end torque a lot like the 5.4 V8 compared to the 3.5 Ecoboost V6. The NA V8’s need more gear to get them in there sweet spot/powerband where they can make torque for the task. I wouldn’t be surprised if you didn’t also get an increase in fuel mileage because I did in the 351, about 2 mpg better on average even when not towing.The old truck doesn’t have to struggle to make power anymore. The best scenario is to have the engine run at highway speeds as close to where it makes most torque in the RPM band as you can.My 2 cents
 

JExpedition07

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When I changed my old 95 F150’s gears from 3.54 to 4.10 it turned into a beast for towing compared to before. But that’s mainly because the 351 doesn’t make great low end torque a lot like the 5.4 V8 compared to the 3.5 Ecoboost V6. The NA V8’s need more gear to get them in there sweet spot/powerband where they can make torque for the task. I wouldn’t be surprised if you didn’t also get an increase in fuel mileage because I did in the 351, about 2 mpg better on average even when not towing.The old truck doesn’t have to struggle to make power anymore. The best scenario is to have the engine run at highway speeds as close to where it makes most torque in the RPM band as you can.My 2 cents

Those 351 Windsors actually made decently good low end torque. Likely was the lackluster transmission in those years that was the problem not so much the motor. The old 4 speeds sapped a lot of power from it.
 
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