I've got a 66 C10 with a 12 bolt rear end. After swapping the straight six for a 350, the diff started popping and chattering. I popped it open, and I'm not sure if I have an open diff that was repaired with posi parts, or if I have a posi unit that's missing parts. The spider gears are definitely posi gears because they have the splined shafts and clutch packs, but it's missing the preload system. Is this a posi unit that I can repair with a summit preloader? Or should I throw it in the trash and just pick up a new posi?