12 Bolt Casting # Help

**COPO** · #1 03-10-2008, 07:05 AM

Have a 12 Bolt for leaf spring car with casting # 3969841 Anyone know what this fits??

**Mr70** · #2 03-10-2008, 07:31 AM

I think you mean 3969341,which came in 1970 Camaros w/12 bolts.

**COPO** · #3 03-10-2008, 05:03 PM

Thanks Rick! I guess that explains why I couldn't find it. Better check my glasses prescription.

**Jeff H** · #4 03-11-2008, 06:24 AM

Got a date and code on that rear? I'd love to grab a COX 3.55 posi housing for my L78 car.

**COPO** · #5 03-11-2008, 04:24 PM

I'll check today.

69L72RS · #6 03-11-2008, 08:27 PM

It could be a late 69 Camaro or a 1970 Nova rear.
Here is what I have determined from the data that I have collected.
1. Late 69 Camaros and 70 Novas shared the STANDARD option CB_ coded housings using the 341NF center casting, for almost all axle codes.

2.

3. 70 Camaros used different codes to differentiate the housing change in size.

The revision from 860NF to 341NF center castings was around late June of 69. I have them being used in housing assemblies as early as the first week of August 1969 in Camaro rears. Hope this info helps.

**COPO** · #7 03-12-2008, 01:15 AM

The casting date is F-21-0. It looks like "BM" then a 1/2" space then "W" then some numbers. Any thoughts on that, not something I've seen before, but looks factory.

**Mr70** · #8 03-12-2008, 01:30 AM

Sounds like a late 70 Nova build or possibly a 1971 Nova 3:31 Open.
W would stand for Warren,Mi. plant.
I had heard these coulda be used a lil longer then 70,as well as used on the Nova too but not sure.
Do you notice the letter C anywhere in front of the BM stamping?
Can you measure the axle tube flange to flange?..is it 54-1/4 or 55-1/4?
Is the measurement between the centerline of the spring seats 42-7/16 or 45-3/8?

**COPO** · #9 03-12-2008, 01:42 AM

Did Novas get 12 bolts in 71? I thought everything was 10 bolt except pontiacs and trucks after 1970.

**Mr70** · #10 03-12-2008, 01:48 AM

Check those measurements I posted and let us know what you find.