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Discussion Starter · #1 ·
Well, I got 16.6 mpg on my trip from Michigan to God's Country (Ohio). The overhead to my surprise matched the hand calc'ed mpg upon fill up.

I drove 65 mph most of the way. If I creeped up to 70, I dropped to under 16 mpg. If I let off to 60 mph, the mpg also dropped. It appears 65 mph is the best speed for optimal mpg on my truck.

Just think if I had 4.56s, AirRam - I'd probably be hitting close to 20! :D
 

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Congrats on your NEW GEARS!!!! Glad to see more people stepping UP in the DODGE world....

Tell us more ... tell us more!

SPEED SAFE, AIR RAM
 

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Discussion Starter · #3 ·
You crack me up! :thatfunny
 

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Jeep Driver
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I think the speed you were driving tells the whole story...... in my '02 Ram with 3.55's and a 360, I get about 20 mpg at 65-70. Anything under or above that range and the mpg is significantly lower.
 

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on my 360 i have been getting anywhere between 14-17 mpg depending on how i step on it and i have the 4.65's for my rig the best speed for milage on the freeway is 65 anywhere over it suffers
 

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Yahh Im stuck on the 65MPH speed limit as well... but I also have the shortest 17's the sold with the trucks, thats not helping anything at all... but Im still able to get great fuel economey at 60-65MPH... so I can live with it in the NAME of PERFORMANCE. Did the 360 come with the 45RFE..?

SPEED SAFE, AIR RAM
 

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AIR_RAM,

First of all, thanks for your in-depth replies with gear info. Your posts helped me make an educated decision when I upgraded to 4.56's.

I was happy with my mpg on my last trip. A 4x4 5.7 pushing 315's at 75-80 mph up and down hills and still getting over 13 mpg is fine by me.

I'll be making the same trip in a week or so, but this time I think I'll work the cruise at 65-70mph and see what happens. I bet 15 mpg is not to far off.
 

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K9Blitz said:
With a 4x4 you have to change both front/rear differentials. I have 315 tires and run about 2200 to 2400 rpm's at 75 - 80 mph.
Dang, I though 4.56 gears would make your MPG suck on the freeway. From what I understand, swapping my 3.92s for 4.56s will not change my MPG much. Maybe even improve it a little. Also, how much did it end up costing you for parts and installation?
 

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BrandonSC said:
With these 4.56s what RPMs you run doing 75-80?
Final gear ratio:


If you have a 45RFE you will use .75
If you have a 545RFE you will use .67

Transmission gear x rear gear of choice = Final gear ratio


Example:


.67 x 4.56 = 3.05

3.05 would be your overall gear ratio.

Find RPM at ANY speed:


SPEED x Final gear ratio x 336 / Tire hight = RPM

Example:

80MPH x 3.05 x 336 / 32" = 2562RPM

I hope this helps.

SPEED SAFE, AIR RAM
 

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what is the round about cost to go to 4.56's including laber and parts?
 

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i found on another thread its around 425 parts and labor..... is this about right?
 

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Charvel350 said:
what is the round about cost to go to 4.56's including laber and parts?

LOL your lucky to live in the DFW area.... Jason at Texas Drivetrain Performance will install gear for 425.00 parts and labor... shop around and you learn real quick that the closest you will find to that is 700+ bucks....

If you need a POSI carrier then the price will be more... but if you have the limited slip then your looking at 425.00

Its important you tell him AIR RAM sent you when you call him.

Here is his Web site:

http://www.txdrivetrain.com/_wsn/page3.html

He can also get parts that MOST other shops can not get.

His address has changed so do NOT use the map on his site... you will get lost!

Give him a shout and let me know what he tells you.

SPEED SAFE, AIR RAM
 

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On the 4x4 Ram what is the size of the front diff? Is it an 8.0 inch and is it an IFS set-up. Thanks.
 

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I average 18 at about 70 to 72 with my 3.92's ON highway of course. Average mpg 13 :eek:
 

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The Doc
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DamnYankee said:
Well, I got 16.6 mpg on my trip from Michigan to God's Country (Ohio). The overhead to my surprise matched the hand calc'ed mpg upon fill up.

I drove 65 mph most of the way. If I creeped up to 70, I dropped to under 16 mpg. If I let off to 60 mph, the mpg also dropped. It appears 65 mph is the best speed for optimal mpg on my truck.

Just think if I had 4.56s, AirRam - I'd probably be hitting close to 20! :D
Yes indeed, God's Country, and still kickin' Maize and Blue bootisimus up and down I-75.....GO BUCKS!! LOL!!
The Doc ;)
 
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