I have an 85' Trans Am that I'm restoring for fun. It originally had a rear end with drums but one of the axles was damaged so I bought a 10 bolt posi from an 89 Camaro (I think). The calipers are stamped with "Made in Australia" and I believe they are PBRs. They would not recess with a C Clamp and did not have slots for the special tool used on some calipers so I pulled the lines at the back of them and recessed them by hand. One recessed well, and went on kind of tight to the rotor (needed to be tapped on) but it works fine. The other side needs about an 1/8" more recession to fit, but the piston hits a very hard stop when I try to recess it, almost like it is fully recessed but I know that cannot be true. Thoughts?

 

If you had to pull the lines, the lines are bad. Replace them.

If they are aluminum, they are the PBRs. "Made in Oz" identifies them as those as well. They don't need the tool thing to retract; the pistons just push in, like front brakes do.

Sounds like the one may have a bunch of corrosion around the piston. Get rebuild kits for them. They're pretty easy to tear down and rebuild. Or, just replace them with rebuilt.

 

Or maybe the guide pins are rusty