Axle ratio vs. mpg
Postmaster
Joined: Jul 2001
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From: South Kitsap County, WA
Why are you swapping? What's the engine size... major use of the truck. It may help in determining if a 4.30 is necessary.
For a 5.4L I'd say overall you can expect 13-15 for a 3.55, 12-14 for a 3.73
You have laid out a loaded question, I'm just trying to steer it away from a "I get way better mileage than you do" discussion.
-Kerry
For a 5.4L I'd say overall you can expect 13-15 for a 3.55, 12-14 for a 3.73
You have laid out a loaded question, I'm just trying to steer it away from a "I get way better mileage than you do" discussion.
-Kerry
Hotshot
Joined: Aug 2002
Posts: 12,679
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From: BC, Canada
Do you do most of your driving in town or on the highway?
In town you might find that lower gears (higher numbers) get better mileage than higher (lower numbers) gears. Usually it's the opposite on the highway unless you're towing.
In town you might find that lower gears (higher numbers) get better mileage than higher (lower numbers) gears. Usually it's the opposite on the highway unless you're towing.
Senior User
Joined: Nov 2003
Posts: 173
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From: Missoula, Montana
While I can't give you any specific numbers for your vehicle, I can tell you my experience with a gear swap.
I used to own a 94 Bronco (full size) 4x4 with a 302/auto, when I put on 33x12.5 tires it really booged down and killed my performance.
So I swapped out the factory 3.55's and installed 4.56's. What a difference in performance.
My Bronco got horrible fuel mileage, 11 mpg no matter what, city or highway.
Going to 4.56 gears improved my city mpg to 12.5; but lowered my highway mileage to 10.5. As my driving is about 80 percent in the city, and only about 20 percent at highway speeds, my overall fuel economy improved as a result of the gear change.
Plus the gear change made the vehicle a real pleasure to drive.
Hope this helps.
I used to own a 94 Bronco (full size) 4x4 with a 302/auto, when I put on 33x12.5 tires it really booged down and killed my performance.
So I swapped out the factory 3.55's and installed 4.56's. What a difference in performance.
My Bronco got horrible fuel mileage, 11 mpg no matter what, city or highway.
Going to 4.56 gears improved my city mpg to 12.5; but lowered my highway mileage to 10.5. As my driving is about 80 percent in the city, and only about 20 percent at highway speeds, my overall fuel economy improved as a result of the gear change.
Plus the gear change made the vehicle a real pleasure to drive.
Hope this helps.
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Mountain Pass
Joined: Sep 2004
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Originally Posted by 2001gocougs
I have a 4x4 F150 Supercab with auto and 3.55ls axle. I am thinking of going to 3.73, 4.10, or 4.30 ratio and would like to know the average mpg.
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Joined: Jun 2004
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I have looked into this also. I tow a campl trailer right around 5000LBS and I have the 5.4 but it struggles in any wind or on a incline. I also do most of my driving at 55 or slower, plus I have oversized tires. So I really think changing the gears will be very beneficial, yet a little expensive. It will be the first mod when I can get the money put together.
Logistics Pro
Joined: Jul 2002
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From: South Dakota
IMO, I think that 4.30's are a bit drastic, 4.10's okay, and 3.73's offer the best mix of both worlds.
Now that I have 285's I've been toying with this idea. Even with my stock 265/70r17s I get better mpg towing my boat at 80mph, than 65mph....If you believe that!!
The difference is that at 65mph I have to pull OD most of the time resulting in 2500 rpms, and at 80mph the motor is wound out enough in OD to pull pretty good and only using 2000 rpms.
I have yet to tow my boat with the 285's but I can't imagine it being any better that the oem size.
This is why I'm entertaining the idea of a 3.73 Ratio, and possibly a 4.10.
Now that I have 285's I've been toying with this idea. Even with my stock 265/70r17s I get better mpg towing my boat at 80mph, than 65mph....If you believe that!!
The difference is that at 65mph I have to pull OD most of the time resulting in 2500 rpms, and at 80mph the motor is wound out enough in OD to pull pretty good and only using 2000 rpms.
I have yet to tow my boat with the 285's but I can't imagine it being any better that the oem size.
This is why I'm entertaining the idea of a 3.73 Ratio, and possibly a 4.10.
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Joined: Jan 2002
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From: Louisville
I have a 99 5.4 150 4x4 with 3.73 gears and I get between 14 and 16 depending on how much highway driving I've done. I don't drive with my foot to the floor and and do about half in town and half on highway. The worst I've ever gotten, even with driving with my foot to the floor, all in town and with a new replacement engine was still 13 mpg. Which is better than I used to get with a 96 150 with a 5.0, the best I ever got with that thing was 12 mpg, doing almost all highway driving. When I do road trips in my current truck I've seen as high as 19 on one tank.
Last edited by robertthompsonjr; Dec 30, 2004 at 02:14 PM.
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Senior User
Joined: Jun 2003
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From: Hawaii
I went with 4.10 gears in my 1999 F150 4.6. After installing 33" tires, it struggled a little when towing my boat. The truck came with 30" tires originally and 3.55 gears. Mileage only dropped about 1 MPG after the switch to 4.10's. It pulls my boat much easier now and is more fun to drive.
Last edited by CPerry; Dec 31, 2004 at 12:40 AM.
Postmaster
Joined: Jul 2001
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From: South Kitsap County, WA
The 4.6 will benefit from the 4.10 swap when towing. The 4.30s should only be used if you're going to go with taller tires (2 or 3 inches taller than stock) and towing. The 3.73s, I feel, may not give you a great deal of towing help. Your talking about a smaller V-8 pulling an amount near its max. Think about the total weight of the combination, not just the trailer weight.
The max rating for the whole setup (including any other payload, yourself and passengers, etc..) is 11,500lbs with factory 3.73s and 17" wheels and 11,000lbs with the 3.55s. The 4.10 was never a factory option in your truck so I'll use an educated guess and say with a higher load rated tire, like a "D," and some stout brakes -ceramic pads and aftermarket rotors- you can probably up that rating by 1000 lbs without any significant problems.
-Kerry
The max rating for the whole setup (including any other payload, yourself and passengers, etc..) is 11,500lbs with factory 3.73s and 17" wheels and 11,000lbs with the 3.55s. The 4.10 was never a factory option in your truck so I'll use an educated guess and say with a higher load rated tire, like a "D," and some stout brakes -ceramic pads and aftermarket rotors- you can probably up that rating by 1000 lbs without any significant problems.
-Kerry
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i have a 98 4.6 5 spd 33" tires. i went to 4.10's and gained about 2 mile per gallon with city driving mostly. when i put the 33 on, it went back to where it was but it is easier to drive as far as not having to downshift as much and it pulls my mustang on a trailer just fine. id go with 4.10's. the 3.73's are only about a 100 rpm difference from 3.55's and for me that wasnt enough. 4.10's were about 450 rpm difference from the 3.55's. i didnt look at your sig but if you have 4wd , i dont think you can get gears for the front. it goes from 4.10's to 4.56's.
Last edited by SHUSTANG; Jan 3, 2005 at 01:38 AM.
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Joined: Jan 2005
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From: Burr Oak, IN
I Have A 4.2 With A 3.08 Rear End-mostly For Back And Forth To Work (90 Mile Round Trip Every Day) And Regularly Get 20-22 Mpg. I Tow Only In The Summer And Have A Trck Camper And A Pontoon. The 5-speed And 4.2 With Mods Does Just Fine. Good Mix Of Economy And Ability To Tow.