Help with 1969 Chevelle 12 bolt axle info

**Too Many Projects** · #1 12-05-2020, 03:35 AM

I acquired a 12 bolt that I just glanced over 3 years ago and recently dug out to repair the shock mounts on. The cast date is June 28, 1968 and initially assumed it was a late '68 build. Today I cleaned off the stamped code and it wasn't assembled until Sept 20th. I got curious and did some www searching and the casting number, 3959038NF comes up as a late '69 axle for high perf engines, which doesn't seem to jive with the assembly date. Also, the assembly code of KF is listed as a 3.55 posi on one website and 3.08 on another.

Any definitive info to identify what the original application and gear ratio code were will be appreciated. It does have the correct Eaton 3 series posi carrier, but has replacement Richmond gears that I can't find any info to decode either. I'm not doing very well with this combo...

Thanks

**L72Chevelle** · #2 12-05-2020, 08:03 AM

KF 3.55:1 ~ 12-bolt Positraction, large ring gear (L35/396, L34/396, & L78/396)* Copied from Chevelle stuff site.

**Too Many Projects** · #3 12-05-2020, 01:12 PM

Quote:

Originally Posted by L72Chevelle

KF 3.55:1 ~ 12-bolt Positraction, large ring gear (L35/396, L34/396, & L78/396)* Copied from Chevelle stuff site.

Yep, that's where I got my info too. They also show this casting number for early '70 with L78. Seems odd that it was cast in mid '68 for LATE '69, early '70 applications. There is a note near the top of that page that states there is a documented axle cast date of December '68. This one is 6 months earlier than that.

Bummer they didn't do partial vin stamp on axles too. Be interesting to know if it sat around for 9-12 months or was, actually, installed in an early '69 with L78...