Gearing help
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Freshman User
Joined: Oct 2008
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Gearing help
Hey guy I have a 05 excursion with a 6.0L. I have a 6pm lift with 35's. I want to change to 37's when I buy new tires. I do pull a very heavy boat now and then. It ways in at near 16k. So I am planning on changing gear ratio. What should I go with? I don't want to low but I do want it to take some of the strain off the trans by changing the gears. I also do a lot of regular driving with the truck. So maintaining some type of fuel mileage would be great also. Any help would be great.
Tuned
Joined: Jul 2007
Posts: 346
Likes: 13
From: Brownstown, MI
What gearing do you have now? I imagine 3.73s? If you are fine with the way it drives now, then upgrading gearing to match the increase from 35s to 37s would only require a 4.10 rear end or so. However, running that big of a tire, I would say go with 4.56s. It will put less stress on the trans than you have now with 3.73s and 35s.
FTE Leadership Emeritus
Joined: Sep 2003
Posts: 12,258
Likes: 769
From: Houston, Texas
I've been through this before and have learned both a hard and expensive lesson....
The proper gearing for 35s WITH a diesel motor is: 4.10
The proper gearing for 37s WITH a diesel motor is: 4.30
Numerically higher and it the truck will noticably lose power at the top
Numerically lower, and you're wasting your money.
The proper gearing for 35s WITH a diesel motor is: 4.10
The proper gearing for 37s WITH a diesel motor is: 4.30
Numerically higher and it the truck will noticably lose power at the top
Numerically lower, and you're wasting your money.
Senior User
Joined: Mar 2010
Posts: 305
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The 6.0 likes to rev and is ok with deeper gears. I have a 6.0 with a 6" lift on 35's and love the 4:30 gears - no more gear hunting. I tow 10500lbs in the mountains and it works great. Fuel economy is a wash as I gained in town and towing but lost on speeds over 60-65mph. If I had to choose again I would keep it the same. If towing flat 4:30 would be ok and put you back to stock gearing and work great on the highway plus would still work with 35's. Go 4:56 if you tow in the Mountains. and don't spend much time above 65mph. Here is a link to a write-up I did on the 4:30 gears - https://www.ford-trucks.com/forums/1...g-results.html
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