The Stovebolt Site Forums The Shop Area Driveline differential & trans id 62 3/4 ton gmc

I have been de-greasing the underside and trying to pull some numbers and see what is original and what has been added along the way.
I know my motor is not original and came from a 61 chevy.

I'm pretty sure that the trans is an SM-420, #'s are ([CON 5, 12 GM, D133, 591953] all on drivers side) and GM II, 591668 on top passengers side. I can't seem to find a date code unless it's D133, but if it is I an't seem to decipher it.

the Differential #'s are as follows if viewing from back of the truck. Bottom of divers side, US. PAT. 2018188. Bottom of passengers side, 80. Top of passengers side, C30255. Top of drivers side, US. PAT. 1338618. Tag on bolt located at the bottom of the drivers side, 41-10 4.10. Also differential had a white X painted on the cover, It was maybe 3x3in, it was painted on, does anyone know what that means? (pic 1)

The trucks rear end is pretty tore back, the shock absorber mounts, and drivers side spring have been welded in (with pretty ugly welds) the passenger side spring looks to be original welds, and a cross-member of the frame is peeled back like 5-6in >.< I'm wondering if that stuff is repairs or if it has all been swapped out with another trucks drive-train.

Thank's for the help in advance

Has a spicer / Dana 60 rear, use in GMCs of the era. Is there a tag on the cover?

tag says 41-10 4.10

If trans is SM 420, hit the Novak site for pictures and descriptions and case numbers. You should find the info needed to id and date.

I've got that same rear end under a 59 Suburban, with a limited slip carrier. The housing came from a mid-1970's GMC. I'm running 3.73 Ford gears and a Dodge pinion flange, since I got the axle given to me with a broken-off pinion and the flange missing. International also used the Dana axle, so there are a boatload of parts available for it.
Jerry

awesome thank you all.

Can be hard to find parts such as brake backing plates, brake drums, etc.