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I have an 03 F350 SCLB. How do I go about figuring out what gear ratio it has in it?
 

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:whs:
or you could pull the diff out and count the teath on the crown and pinion and do the math. but i would look for the tag.
 

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Yeah, it's like that
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:whs:
or you could pull the diff out and count the teath on the crown and pinion and do the math. but i would look for the tag.
Before you go taking off the diff cover, if the tag is missing, go see what the truck is running at 60 mph for RPM in drive. You can calculate it out. If you need to know, post up rpm and tire size, I can tell you what gear you have
 

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TimmyaleX
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:whs:
 

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Before you go taking off the diff cover, if the tag is missing, go see what the truck is running at 60 mph for RPM in drive. You can calculate it out. If you need to know, post up rpm and tire size, I can tell you what gear you have
I wanna know your calculations :) 265/75/16 70mph 2100rpm
 

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Most likely a stock rear end with a 3.73 or a 4.10. Lift both rear wheels, in neutral, chalk mark driveshaft and tires, count driveshaft revolutions (more or less than 4). Not perfect but very close and easy to do.
 

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Yeah, it's like that
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I wanna know your calculations :) 265/75/16 70mph 2100rpm
The formula is right here:

http://powerstrokenation.com/forums/showpost.php?p=957581&postcount=4

This was on a truck that had the 4R100 which has a final drive of .71:1. Your 04' has a 5R110W which also has a final drive of .71:1 your truck has tires that are 31.65" in diameter which have a circumference of 99.38" which would have to rotate 685.85 times in a mile. So at 60 if you had 3.73 it would be as follows (685.85 x 3.73 x.71=1816 RPM) or for 4.10 it would be as follows (685.85 x 4.10 x .71=1997 RPM)

Since you can't follow my previous post of what RPM and tire size at 60 mph and you chose to post 70 mph now we have to do another calculation

1816 RPM /.857= 2119 RPM at 70 MPH for 3.73

1997 RPM /.857= 2330 RPM at 70 MPH for 4.10

You have 3.73's

:popcorn:
 

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OEM 4.10s were only found in the gas motor versions. More than likely if it's stock you got 3.73's installed. The axle tag will tell you for sure.
 

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OEM 4.10s were only found in the gas motor versions. More than likely if it's stock you got 3.73's installed. The axle tag will tell you for sure.
I have OEM 4:10 and a 6.0L diesel, I know they are original as well because I picked up the truck from the dealership with 19 miles on it.
 
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