I've done a lot of looking and haven't come up with an answer so I'm coming to the experts. I'm going to need to have some work done on the rear end of my '56 3100. It has a roar at lower speeds. I believe it is not original to the truck so here is a picture and the code appears to be KAS 137W87. There's also a small lettering higher and to the right that appears to be something I can't identify that looks like ?-H Oh yah, it's a 12 bolt.
More info...casting numbers on the rear end: 3896890, GM86, N
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20240507_104949.jpg (204.63 KB, 81 downloads)

Last edited by MickeyP; 08/22/2024 6:47 PM.
1956 3100 three speed 6 cyl. Stock with a few upgrades.