Gear identification without RPO

[0RESET0]

I can't believe that this has never been discussed before but I could not find it thru search. Is there a way to know what gears a TB has if the RPO tag is gone? I will be headed to a junk yard in the next couple weeks to get a front axle disconnect to rebuild and swap into my truck. While I am there I thought I might see if any of the trucks have 4.10 gears. So, is there any way of knowing the ratio other than the RPO code such as an axle tag? If so what am I looking for? Simple tag with 410 stamped into it or stamped into the housing?

[The Roadie]

You take the cover off and count the gear teeth, or turn the input pinion while keeping one axle from moving, and count the rotations of the other axle. The empirical test (just rotating the thing and doing the math) has been discussed a bit here, but I bet you can find a Youtube video. Just reflect for a short time on what a GEAR RATIO means, and the way to figure it out should become obvious.

[0RESET0]

So what you are saying is that GM no longer marks the differential housings with the gear ratio they were originally assembled with.

[v7guy]

I haven't seen a tag showing the installed gears in quite some time