Gears
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Joined: Jun 2021
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Gears
I have a 62 F100 2WD short bed it has a 390/C6 9" rear end ill be daily driving it. I'm doing the rear end now it's getting a truetrac but I'm torn between 3.00 or 3.25 gears. What are your thoughts?
Logistics Pro
Joined: Jun 2018
Posts: 3,549
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Most folks go to a higher gear ratio to keep the rpm's down on the highway. The major problem with that is acceleration and gas mileage suffers due to the motor working harder to get and keep it moving. I still run the 410's in my 66 and would never change them. My 2020 Tundra has 430's with 35" tires and it drives like a dream. Granted it has 2 overdrive gears. If you still want performance and lower rpm's on the highway focus on the transmission upgrade and keep the rear at 350-380 range.
Fleet Owner
Joined: Jun 1999
Posts: 24,552
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From: Creedmoor, North Carolina
The FE will supply plenty of power, but it is a gas lover. I recommend the 3.00 to keep it turning as slow as possible on the road. I also recommend the smallest 4 barrel for better fuel mileage. A few years ago I was stopped by highway crew working on a bridge. There was a long fairly steep hill in front of me. When I started, I floored it and was running past 100mph when I got to the top with a 3.00 rear. When running high number ratios meant for the smaller engines you will litteraly have raw gas running out the exhaust pipe. IMHO 
John
John
Mountain Pass
Joined: Nov 2013
Posts: 200
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From: Mason City, IL
I agree with John. I have a 390 w/the 3.03 manual and went with 3.00 limited slip rear. Fine on city or highway. Carb is Edelbrock 4 bbl 600 CFM. With that said, this winter I'm going to Holley Sniper EFI and a Tremec T5 and keep the 3.00 rear end (for now).
Mountain Pass
Joined: Aug 2017
Posts: 114
Likes: 43
The math is easy on rear axle ratios. All you need to do is measure your rear tire and you can figure out the RPM at a given speed. Then just play around with it. Look at what common speed you will be doing and where the motor runs happy. Always check your first gear. You don’t want it so high that it has to work hard off the line. Here is a link to a calculator = Online transmission rear axle ratio calculator
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