BE 12 bolt questions

[Fast67VelleN2O]

Alright so the posi unit is just a standard unit. Guess I am going to separate the gears from it.

I was also puzzled by the date spread Albert.

[69L72RS]

The date difference is fine as long as the gears are a mated (lapped) pair/set.

When the gears were made, they were produced in equal order quantities. I'll use 100 for the example, as it was explained to me.
The gear plant created an orders for 100 pinions and 100 rings.
During production one more of the ring gears got damaged/scrapped. So there would be extra pinions.
The extra pinions sit in surplus until:
1) An extra ring becomes available from a later production run, do to damaged pinions, to allow a set to be paired/lapped.
2) Enough of them piled up justify a balancing order quantity to be produced.

I was told that the r&p sets only left production as paired/lapped sets.

I have several NOS and used sets that are mixed dates. I think the largest spacing I have is from 11 67 to 5 68 for a 3917971 r&p set.
Hope this helps.
Eric

[Fast67VelleN2O]

Yes this is a matched set out of the same rear end.

Thanks for the information guys!

[TXSS]

Wile we’re on the subject of COPO ring and pinion gears. This is a set of what I believe to be 4:56 COPO gears. I got these with an 0428 BE. My question is why the difference in the stampings and the location of the stamping on this set of COPO gears vs the set shown in the previous pictures. Was this a service replacement set. Eric, anybody, any idea.

[69L72RS]

Rick,
Yes those are COPO 4.56 gears p/n 3917973.
They are service dated gears from 1975.
From what I have been able to determine anout the different makings and locactions is that gears like these were made at a different plant than the original production gears.
Here is a set of COPO 4.10s from 1974. that match your 4.56s.
I will post pictures of the different markings that I have found this weekend.