D60 gearing

[1987Blazer]

How do I tell what gearing is in my D60 The tag on the diff cover has 41-10 and 4.1. the gear also had 41-10 on the edge of the gear along with a bunch of other #s.
Also 3 of the teeth have some surface rust I think it is on top of the gear should I worry about it?
Thanks
Steve

 

[K588]

You have 4.10 gears- divide the 41 by 10 and it gives you your ratio.