help me id 12 bolt please

[harry]

pass side housing has 3896839 NF, Drivers side housing has GM51 and pass side axle tube has MS1207W2 with a slanted E underneath that bunch of letters and numbers, cheers

[Captainfab]

There are a bunch of the differential codes in this thread.

http://67-72chevytrucks.com/vboard/s...d.php?t=327764

I don't remember if the build code is at the begenning or at the end of the stamping on the passenger side axle tube, since I typically don't bother with them. I just pull the rear cover and have a look. Who knows what has been done in the past 48+ years.

With that said, the only MS I see is for a Eaton HO52/72 with 5.14 gears.
Is it possible that the W2 at the end is actually a WZ? That would be a 4:11 positraction from a '63 G10 van. The other option is that it is a '67-'72 12 bolt since the listing shows just a little of the '67 codes.

[harry]

thanks for that captain will pull the cover that's probably best cheers