12 bolt didferential gear ratio identification

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xm20k

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David
Truck Year
78
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c10
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hey mister

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Marty
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350
The code is stamped on the top passenger side axle.
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Where did you find thst printed info.?
 

xm20k

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c10
Engine Size
388
Took a while to remember where I saved this.

First 2 digits
1973

2.73..............WA
2.73..............AC
2.73 posi........XB
2.73 Posi........CC
3.08..............WC
3.08..............AD
3.08 Posi........XC
3.08 Posi........CD
3.42..............WE
3.42...............AJ
3.42 Posi.........XE
3.42 Posi.........CJ


1974

2.73..............AC
2.73..............CC
2.73..............WB
2.73 Posi........XA
3.08..............AD
3.08 Posi........CD
3.08..............WC
3.08 Posi........XC
3.42..............AJ
3.42 Posi........CJ
3.42..............WE
3.42 Posi........XE


1975

2.56 posi........CH
2.56..............AH
2.73..............WA
2.73posi........XA
2.73posi........CC
2.73..............AC
3.08..............WC
3.08 posi........XC
3.08 posi........CD
3.08..............AD
3.42..............WE
3.42 posi........XE
3.42 posi........CJ
3.42..............AJ


1976

2.56 POSI........CH
2.56 POSI........AH
2.73...............WA
2.73 POSI........XA
2.73 POSI........CC
2.73...............AC
3.08...............WC
3.08 POSI........XC
3.08 POSI........CD
3.08...............AD


1977

2.56.............AB
2.56 POSI.....CB
2.73.............ZE
2.73.............AC
2.73 POSI.....ZW
2.73 POSI.....CC
3.08.............ZJ
3.08.............AF
3.08 POSI.....ZY
3.08 POSI.....CF
 

xm20k

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Joined
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Location
Girard, Ohio
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David
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78
Truck Model
c10
Engine Size
388
Where did you find thst printed info.?
Don't remember saved it a while ago. Was planning on rebuilding and regearing the 12 bolt that was originally in my truck but decided it was less hassle to just buy a new 9 inch housing with axles that was already built with the flip mounts on it and a spooled center section with the gears I wanted and just change the yoke for a billet 1350.

https://www.speedwaymotors.com/73-8...ing-With-Axles-Flipped-Mount-Pads,488090.html

https://www.speedwaymotors.com/Ford...pool-31-Spline,2198.html?sku=91048343-457-STD
 
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