Gearing
Moderator
Joined: Jul 2010
Posts: 12,064
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From: Media PA
Do you tow at all with the EX?
My EX back when all stock with 3.73s would get 15/15.5 MPG on an all highway run, now with the 4" lift, 4.88s, 35"s (effective 4.39 ratio), headers and tunes (last two don't affect mileage very much at all) it gets 12.5 MPG on the highway, most of that loss is from the tires and lift I think. Others have reported about a 1 MPG drop on highway mileage with no other changes than going from 3.73s to 4.30s and some have seen a slight increase in city mileage with the same swap. Towing mileage should increase with deeper gears, mine did by about 20/30% depending on the trip.
Mountain Pass
Joined: May 2011
Posts: 222
Likes: 11
From: Strasburg,CO
I only two on occasion and it's rare. I live and drive pretty much @ 5280 feet above sea level (that's 1 mile high) I'm sure the elevation has a bit to do with it but I was getting 13.5 mpg on flat and 12 on 3% or less grade. Now I get 9 to 10 flat and 7 to 8 on small grade or if the wind is blowing in my face. I like to offroad in the Rockies and climbing I70 from golden Colorado has become a bit of a workout for the trans. I use to be able to drive this stretch of road and never come out of overdrive with cruise control on @70. I want to get close to that again.
Mountain Pass
Joined: May 2011
Posts: 222
Likes: 11
From: Strasburg,CO
I only two on occasion and it's rare. I live and drive pretty much @ 5280 feet above sea level (that's 1 mile high) I'm sure the elevation has a bit to do with it but I was getting 13.5 mpg on flat and 12 on 3% or less grade. Now I get 9 to 10 flat and 7 to 8 on small grade or if the wind is blowing in my face. I like to offroad in the Rockies and climbing I70 from golden Colorado has become a bit of a workout for the trans. I use to be able to drive this stretch of road and never come out of overdrive with cruise control on @70. I want to get close to that again.
Moderator
Joined: Jul 2010
Posts: 12,064
Likes: 1,574
From: Media PA
I only two on occasion and it's rare. I live and drive pretty much @ 5280 feet above sea level (that's 1 mile high) I'm sure the elevation has a bit to do with it but I was getting 13.5 mpg on flat and 12 on 3% or less grade. Now I get 9 to 10 flat and 7 to 8 on small grade or if the wind is blowing in my face. I like to offroad in the Rockies and climbing I70 from golden Colorado has become a bit of a workout for the trans. I use to be able to drive this stretch of road and never come out of overdrive with cruise control on @70. I want to get close to that again.
Have you recalibrated your PCM for the new 35" tires? If not, your speeds and mileage are off by about 12% or so on the low side due to the taller tires.
Higher elevations rob power on NA gas engines, that along with the 35"s and running off road in the mountains all sound like even more reason to go with a deeper gear than your proposed 4.30s.
Mountain Pass
Joined: May 2011
Posts: 222
Likes: 11
From: Strasburg,CO
no longer in New Jersey. Now in Colorado. I have not done the recalibration yet. When I'm doing 70 I'm at 2140rpm with overdrive on. I'm just not sure if 4:30 is the right gear. I would like to put 37's under the X when my new tires need to be replaced. That is my delemma.a
Moderator
Joined: Jul 2010
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From: Media PA
Gear swaps are expensive and you don't want to have to do it twice, if 37" are a future possibility then go with 4.88s. With the 35"s you will have an effective 4.30-ish ratio, which is the "sweet spot" for these engines and if you later go up to 37"s then the effective ratio will only drop to about 4.10, both will deliver better performance than the factory 3.73s.
Moderator
Joined: Jul 2010
Posts: 12,064
Likes: 1,574
From: Media PA
Is that 2140 RPMs at 70 MPH on the (now incorrect) speedo or by GPS? With my 35.28" tires and 4.88 gears (effective ratio of 4.39) it's turning 2400 RPMs at a GPS verified 70 MPH. Some folks worry about the deeper gears causing the engine to rev too high on the highway and don't want it to be screaming at cruising speeds, when I was running the 4.88s with 32" tires (nearly stock sized) it was still only spinning at 2600 RPMs at a GPS 70 MPH.
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Trailering
Joined: Aug 2008
Posts: 17
Likes: 0
From: Orlando
Is that 2140 RPMs at 70 MPH on the (now incorrect) speedo or by GPS? With my 35.28" tires and 4.88 gears (effective ratio of 4.39) it's turning 2400 RPMs at a GPS verified 70 MPH. Some folks worry about the deeper gears causing the engine to rev too high on the highway and don't want it to be screaming at cruising speeds, when I was running the 4.88s with 32" tires (nearly stock sized) it was still only spinning at 2600 RPMs at a GPS 70 MPH.
Just had a trip to West Palm and at 75 MPH (GPS) she was turning just a tad over 2000 RPM’s on 35” tires with the stock gearing. Oddly the lieometer and my math agreed at approximately 11 MPG, give or take a tenth.
Gear swaps are expensive and you don't want to have to do it twice, if 37" are a future possibility then go with 4.88s. With the 35"s you will have an effective 4.30-ish ratio, which is the "sweet spot" for these engines and if you later go up to 37"s then the effective ratio will only drop to about 4.10, both will deliver better performance than the factory 3.73s.
Mountain Pass
Joined: May 2011
Posts: 222
Likes: 11
From: Strasburg,CO
Is that 2140 RPMs at 70 MPH on the (now incorrect) speedo or by GPS? With my 35.28" tires and 4.88 gears (effective ratio of 4.39) it's turning 2400 RPMs at a GPS verified 70 MPH. Some folks worry about the deeper gears causing the engine to rev too high on the highway and don't want it to be screaming at cruising speeds, when I was running the 4.88s with 32" tires (nearly stock sized) it was still only spinning at 2600 RPMs at a GPS 70 MPH.
Mountain Pass
Joined: May 2011
Posts: 222
Likes: 11
From: Strasburg,CO
Gear swaps are expensive and you don't want to have to do it twice, if 37" are a future possibility then go with 4.88s. With the 35"s you will have an effective 4.30-ish ratio, which is the "sweet spot" for these engines and if you later go up to 37"s then the effective ratio will only drop to about 4.10, both will deliver better performance than the factory 3.73s.
Token Redneck
Joined: Jun 2007
Posts: 9,339
Likes: 350
From: Breckenridge, TX
I used to live in Denver. Call these guys, big shop over off 85 and Hampden in Englewood:
High Country Performance 4x4 - Off Road Truck Parts
You doing traction aids at the same time? I did some pretty mundane stuff in a Ranger and stock F250, nothing that would needs 37s and lockers, but there's a lot of good places up in the mountains.
High Country Performance 4x4 - Off Road Truck Parts
You doing traction aids at the same time? I did some pretty mundane stuff in a Ranger and stock F250, nothing that would needs 37s and lockers, but there's a lot of good places up in the mountains.
Logistics Pro
Joined: May 2017
Posts: 3,523
Likes: 483
From: Southern OH
What do you mean by FX4 rear? It won't be cheaper to get whole new axle then it will be to put an auto locker in the rear. I love my Detroit locker and the Yukon Grizzly locker is also very good.
Mountain Pass
Joined: May 2011
Posts: 222
Likes: 11
From: Strasburg,CO
I had a f350 fx4 and there is an auto locker in the rear. I find them on craigslist and other sites for 300 and up. The average price is 800. I did find one that was 400 with 4:30's but I didn't have the cash at the time. If I buy the ring and pinion the locker and the master rebuild kit then have it installed it's over 1000. Buying a rear would be cheaper then I sell mine and save even more $.