Rear Diff ID

[blublazn86]

In my quest to decode the rear diff in my 87 R10 2wd square body I have hit a wall!!  The RPO tag has a code of Y03 which shows to be a 7.625 ring gear Saginaw/American axle but I can't find out any other info on what the factory gear ratio would be.  I got the casting code off the axle its self and it reads as follows  BS3 G093 and there is a casting code on the center section or (pumkin) that is C307.  Every where that I have looked I have came up empty handed so I am asking for the help of my fellow bowtie builders out there.  Any and all help is apperciated!!  Thank you!!!

[pholliday1]

****IF**** it's stock its a 10 bolt, the numbers that tell you what your gear ratio is, is "SUPPOSED" to be on a metal tag bolted To the cover, which is "probably" long gone. So the only way really to figure it out it to pull the cover and count the teeth. Also you will be able to tell what type of differential you have, open, posi or locker. Best bet post a picture of the pig(pumpkin)

[Captkaos]

ALL 1987 pickups use the 8.5" 10 bolt rear diff.
Not sure what Y03 is, would have to look it up, but it isn't a 7.6 ring gear.  Generally this is a seat option.  Like folding or non folding.

If  you post the G numbers and the VIN I tell you what came with it stock, but only way to know for sure is if you pull the ring gear.

[blublazn86]

The only "G" letter on the RPO list is GL3 or possibly GU3  but it does not show a definition of what it would mean it's blank

[Captkaos]

If it is a 1987 1/2Ton R series the only codes would be GQ1, GU4, GU5, GU6 and GT4.
And what GQ1 (which is standard ratio) could be depends on the drivetrain.

Even with all this info, it doesn't guarantee your ratio, it only show what would have came in it.