Dana diff ratios
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Cross-Country
Joined: Apr 2017
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Dana diff ratios
Hi all after doing a few hundred miles at xmas and stopping at every gas station i saw I'd like to improve the mpg. Currently has 4.1 dana what other ratios are available for dana diffs. Thanks
Logistics Pro
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Dana 60 rear. If I remember correctly 3.73 is the highest your carrier will take. I have the same set up and get 14mpg 2800rpm @ 70mph with a mild cam 410ci. Gear vendors have overdrive units that might be a better option for highway use.
Ford Parts Specialist
Joined: Nov 2006
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From: Simi Valley, CA
You may have to change the companion flange to match the splines of the ring and pinion you use.
10 splines: 4.88-1 (1955/66); 4.56-1 (1956/66); 4.10-1 (1963/66).
29 splines: 3.54-1 (1966/72); 3.73-1 (1967/72); 4.10-1 (1966/72).
Differential case is the same: 3.54/3.73/4.10.
Logistics Pro
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From: PHX AZ
my ‘66 F250 I changed to 3.54 and added a Dana Posi. I also have a 6 spd auto trans so it should do well.
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Logistics Pro
Joined: Feb 2011
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From: Townsend, MT
Typical answer for a the question of "what's the highest gear a Dana 60 can take?" is 3.54:1. Decent gear for a mild FE running 30" + tires at 55 - 60 MPH.
With a little machine work, 3.33's and 3.07's can be installed.
I run 3.33's in my old heap with 32" tires and will get between 10 and 12 MPG running 80 MPH weighing 8000 LBS. She cruises really nice at 65 - 70 MPH.
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Below 2000rpms your using more throttle to maintain speed or accelerate. The vacuum drops right off at low rpm acceleration. That's why when your going 30 in 3rd and you step on it you have a very short burst then everything goes flat and you wait for the vacuum to start sucking on that carb again. The sweet spot on the Fe's is from 2800 on. On the road the vacuum gauge is the way to go if you are worried about MPG's
Logistics Pro
Joined: May 2008
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From: PHX AZ
Below 2000rpms your using more throttle to maintain speed or accelerate. The vacuum drops right off at low rpm acceleration. That's why when your going 30 in 3rd and you step on it you have a very short burst then everything goes flat and you wait for the vacuum to start sucking on that carb again. The sweet spot on the Fe's is from 2800 on. On the road the vacuum gauge is the way to go if you are worried about MPG's
My bone stock Ranger with 3.25 gears and factory Overdrive does fantastic right off idle. As soon as Truck is rolling it’s in 2nd gear then usually in high at 2000 rpm. Into high OD by 40 mph.
Logistics Pro
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I thought we were talking about MPG. I live in the mountains so my perception of roll on power vs economy is different from flat roads. I know that when I roll on 1500rpm in third gear your not going to go much faster anytime soon, Down shifting to bring the rpm's up to do that is much more efficient.
Cargo Master
Joined: Apr 2001
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From: Vancouver
The 3.54 that Boss mentioned is a good compromise. The few I have seen were in CS trucks with the 460/C6 combination. Those I saw were all limited-slip. A skinny radial-ply tire in the original diameter would help as well, but not many of those are made anymore.
Eric
Eric
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I found this in a physics form:
Cars are mostly designed to be most efficient in the highest gear while at normal highway speeds, but this characteristic is not intrinsically true of engines.
Note that the best fuel economy for a given power requirement does not always occur at the lowest engine speed. For an output of 50% of the maximum horsepower of the engine, the most efficient operating point is about 63% of the maximum RPM - at 102% of the minimum fuel consumption. =left
=left
Reference https://www.physicsforums.com/thread...ileage.165455/=left
Cars are mostly designed to be most efficient in the highest gear while at normal highway speeds, but this characteristic is not intrinsically true of engines.
Note that the best fuel economy for a given power requirement does not always occur at the lowest engine speed. For an output of 50% of the maximum horsepower of the engine, the most efficient operating point is about 63% of the maximum RPM - at 102% of the minimum fuel consumption. =left
=left
Reference https://www.physicsforums.com/thread...ileage.165455/=left
Logistics Pro
Joined: Feb 2011
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From: Townsend, MT
Below 2000rpms your using more throttle to maintain speed or accelerate. The vacuum drops right off at low rpm acceleration. That's why when your going 30 in 3rd and you step on it you have a very short burst then everything goes flat and you wait for the vacuum to start sucking on that carb again. The sweet spot on the Fe's is from 2800 on. On the road the vacuum gauge is the way to go if you are worried about MPG's
Typical FE will hit peak torque around 2200 - 2400. Set it up so you are running 2200 ish @ 70 in a 2 wheel drive pickup and you will see some decent mileage numbers. 1500 to 1700 RPM @ 55 is ideal IMO.
As for cruising at 2800 RPM, that is nuts unless you have a well built FE and consider "cruising" to be 80+ MPH and have a vehicle in excess of 8,000 Lbs.
Come to think of it, My 8500 pound 4 wheel drive pig cruises really nice at 80 MPH turning 2800 RPM - but like you say, when I wind her up to 90 (about 3100 RPM) she really starts to come alive. Thera again, I have an FE that is hotter than most, am mostly nuts, and cruise between 80 and 90.
I'm planning on taking the flatbed and most of my tools off Old Green and swapping them onto another pickup and then building a nice light wood bed this winter. If I ever get my 19.5 wheels, I will be stepping up to 34" tires at the same time. This should set me close to 6,000 pounds and 2600 RPM @ 80 - I'm thinking I may see some decent mileage numbers.