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Discussion Starter #1
I don't know what my gear ratio is on the rig. Everything is in the sig, I tried the conversion but can't see anything stamped on the diff. cover, and on the door where it says "Axle" there is no number ....

I can tell you this though, at 55mph I'm at about 1800rpm, and at about 71mph I'm at about 2600 rpm. Both on fairly flat road.

4.10's? I dunno how to figure it out :( :dunno:
 

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Discussion Starter #2
Nobody? No guesses? I just wanna know.
 

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and on the door where it says "Axle" there is no number ....

There is no axle code like C2 or the like??
 

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i have 4.10s and when im going 70 im at 2250 rpms or a tad less actually
 

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Discussion Starter #5
i have 4.10s and when im going 70 im at 2250 rpms or a tad less actually
That's more like what I meant. It's not quite 2600 I don't think. My bad.
 

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Discussion Starter #6
and on the door where it says "Axle" there is no number ....

There is no axle code like C2 or the like??
Right, I didn't see any number there. But I'll look again next week when I'm around the truck.
 

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Discussion Starter #7
I also don't know what trans is in it. I'm pretty curious of that too. Good thing to know lol
 

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I have an 03 with 4.88 rear I turn about 2700 at 75mph. Then again I have an F550. I have been wondering what it would do if I switched the 4.88 to a 4.55 what that would do to my mileage. I get 13mpg now.
 

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4R100 trans. Gear ratio you would have to give us the code on the door. Or remove the diff cover and read the stamp on the ring gear. It is there trust me on that. Only problem is you would have to change your diff fluid at this time as well. Or you can mark the driveshaft, mark the tires. Put the rear on jackstands. Chock block the front tires so the truck won't roll, put the trans in nuetral and spin the tires. Count how many revolutions the driveshaft makes for 1 revolution for the tire. This will give you a pretty good idea on what gear ratio you have.
 

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What weight gearlube for the rear?:)
 

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i thought all DRD had 4.10's?
 

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My dually was originally geared 3.73s and turned 2000 rpm at 70 mph. Now I changed the ratio ti 4.10s and at 70mph it turns about 2250 rpm.
 
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