Help With Gear Change
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Joined: Sep 2010
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Help With Gear Change
I have a 1996 Regular Cab Long Bed F-150 4.9L with a 3.55 rear end. I drive around a 1000 mile per week and get about 18-19 mpg driving 50-55 mph. I tow a small trailer (< 3000 lbs) less than 20 miles per week. I don't have money for a new truck, but need to get better gas mileage. I am trying to find out how much I can change my gears, whats the smallest I can go with, approx mpg change. I saw a chart that showed ford having a 2.73 in f-150 regular cabs in '91... thinking this would be a good fit...
Super Moderator
Joined: Apr 2004
Posts: 34,499
Likes: 2,811
Find out your transmission ratios and tire size, and put the numbers in here along with your current and possible ratios.
Novak Conversions - Gearing & Gearing Math for Jeeps
That will tell you the mph/rpm numbers, and you can figure out if it will pull a particular gear or not. Nothing goofs this up like the inability to pull OD, and now even though you have a higher speed axle, you are stuck in a lower gear and are running the same or more RPM as before.
Also, figure out how much money you will save if you get a 20% improvement in mpg--which is not likely. You are probably looking at 2 years to pay this back, depending on your miles per year.
Novak Conversions - Gearing & Gearing Math for Jeeps
That will tell you the mph/rpm numbers, and you can figure out if it will pull a particular gear or not. Nothing goofs this up like the inability to pull OD, and now even though you have a higher speed axle, you are stuck in a lower gear and are running the same or more RPM as before.
Also, figure out how much money you will save if you get a 20% improvement in mpg--which is not likely. You are probably looking at 2 years to pay this back, depending on your miles per year.
Post Fiend
Joined: Mar 2002
Posts: 19,402
Likes: 38
From: Bonita Springs FL
If you're getting 18-19 MPG in a pickup truck with 3.55 gears, don't touch a thing. You should be thrilled. You will never get better mileage than that. Going to 2.73 gears will absolutely kill the towing performance of the truck, and it could actually decrease your mileage because now the engine has to work a lot harder to get the truck moving. Plus you will need to downshift to get over any kind of hill. 2.73 is a car ratio, don't put it in a truck.
