gear ratios

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Jan 10, 2008 | 12:31 AM

theguy_88

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gear ratios

i bought a ford, f-350, 4x4, powerstroke dsl, auto,single wheel, with a 8 inch lift and 38. i am thinking i am going to change the gear ratio. right now at 65mph it revs 1600rpm. i would like to know what they rev stock and where the best place rev to get the best fuel milage is? and also what the ratio in the top gear in the trans is?

Jan 10, 2008 | 02:30 AM

Monsta

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From: Washington State

.71

My calculations say you have 4.10s. What year is your F350????? SRW didn't have 4.10s except some years of DRW. Course the RPM gauge isn't always super dead-on accurate. If stock, you've got 3.73s

Stock with 3.73s should put you around 1830RPM at 65mph with stock 31.6" tires.

To get that with 38's you'll need to regear to 4.56's. Best for mileage would be 4.30s.

http://www.angelfire.com/space/slr/RPMCalculator.htm

Last edited by Monsta; Jan 10, 2008 at 02:32 AM.

Jan 10, 2008 | 07:07 AM

Green Ford

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From: Raleigh, NC

This may help some too.
http://www.4wheelparts.com/gear_ratio.html

Jan 10, 2008 | 11:53 PM

theguy_88

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my truck is a 2005 and i put some banks powerpack with the fuel saver on my truck that is where i get the rpms from and it helped with fuel milage, but still can get some more fuel milage out of it and still have drive abitity. one move problem is that it says that the tires are micky tomson 38x15.5 and im not how close that is, so i am going to pull of he diff cover and and count the ring and pinion the see if the gear ratio was changed the sticker says that it was 3.7? the last digit was missing but i was guessing it was a 3 . and to be truthfull i usualy drive 70 mph so what is the better ratio? and to find the gear ratio after counting the teeth you divide them in to each other i havent done this in a wile?

Last edited by theguy_88; Jan 10, 2008 at 11:56 PM.

Jan 12, 2008 | 04:02 PM

theguy_88

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no one has ansered the question where did the engine rev when the truck was stock and where it should rev to get good fuel milage any help is apprecated

Jan 12, 2008 | 04:07 PM

biz4two

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From: Albuquerque

Quote:

Originally Posted by theguy_88

no one has ansered the question where did the engine rev when the truck was stock and where it should rev to get good fuel milage any help is apprecated

Actually here is the quote from Monsta...

Quote:

Originally Posted by Mosta

Stock with 3.73s should put you around 1830RPM at 65mph with stock 31.6" tires.

There yozz go...

biz

Jan 12, 2008 | 09:38 PM

b2jrg

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Rear diff

I just purchased a 2006 F-350, 6.0. Automatic. The door information sticker says that it is a 4N rear end. Is this a 3.73 or a 4.10. I just drove it today on the interstate for about 400 miles and the mileage was an unbelievable 19mpg.
I cannot find any thing on the internet regarding the 4N classification. Thanks