I need help de-coding this rearend on the right side it is stamped GM77, on the left side it is stamped 3969440NF
Any help would be appreciated.

This doesn't seem to be a good number Ruben. Post a picture of the casting number and the numbers/letters stamped on the passengers side axle tube.

Ed

The #'s on the passenger side axle tube reads GR W040 1. On the back side Passenger side it reads 00N2 On the back side drivers side it reads A151. And stamped on the pasenger axle it reads 9348 FX. I know this is not the factory rear end I was just trying to figure out what it came out of.I am restoring a 69 RS Camaro and no it is not a factory restoration. So thanks for your help.

Okay, that helps. You have a 1971 Nova 3.08 non-posi 10 bolt axle. The center section was cast on January 15, 1971 (A151) and the axle was built at the Warren, MI plant on Tuesday, February 9th, 1971 during the first shift (W040 1 GR).

Ed

Thanks alot for your help!! Now I know some history on this part of my car. The rear end has an Auburn positive unit and 373 gears now. Or at least that is what the last owner told me.Again thanks for your time and your help!