[Toby Hines]

Im having issues with a C10 12 bolt and I need to pin down the year. Casting code is 3856525 and Axle tube # HA 02 18W. I know its a 3.73 open diff.

This rear has barely any room outside the Main caps for shims. I know 12 bolts usually have thick shims. This one had only a .083 on right side and a .073 on left and the main caps dont have a little tab on the upper out side to hold the shim down. The problem is I purchashed this rear and went to do a fluid change and noticed the thin shims had slid out and hit the rear cover and ground into the Axle. I want to freshen this up. I even went as far as pulling off a carrier bearing to check the part number to verify it had the correct bearings. Ive never seen these small shims in these. I was told 60-61 rears were bastard years and used shims under the carrier bearings and also told these early year 12 bolts had pressed on backing plates, this one has bolt on backing plates. Im hoping to use this rear. the other issue I cant find replacement shims and even if I do theres nothing to hold them down other than a tight fit at install. What gives????