I am decoding my POP and figured it all out o.k. except for my rear axle. The code is : cou06237 -cou= 3:31:1 non-posi, 0623= June 23rd, 7=?????
I though the last digit (normally a letter) was supposed to be the plant.
Can anyone explain this?

I'd guess the POP is misstamped. Check your axle and I'm guessing you will find that last digit is a G, not a 7.