I recently put new pads and rotors on the rear of my '95 Z. Now.. when I turn left, I get a brake squeal from the right rear.... I noticed some old oil residue on the inside of the old rotor like the axle seal had leaked at one time. I think my Diff vent had been plugged.. and I've since cleaned it out.
With the way it's only squealing when I make a left turn.. it's almost like the axle is moving in the housing (flexing) and causing the rotor to touch the bad when cornering. I shouldn't say cornering, pretty much if I'm making a left turn. It is possible the axle bearing on that end is so worn out that the axle is moving around?

It has 210k miles on it.... I changed the diff fluid recently.. everything around the pinion looked good.

 

Here is the solution.
One or maybe both of the rear rotors is rubbing a rear caliper bracket. I can almost guarentee this is causing the noise, it happens on LT1 rear brakes a lot.

There are two fixes.
The first is to remove the caliper bracket from the axle (2 bolts) and slide the bracket off off the caliper (just slide it off).
If you look closely at the bracket you will see the spots where the rotor is rubbing, you will also see the circular marks on the rotor too.
Get the disk grinder out and clearance the bracket in the areas where the contact is occuring and reassemble. I had to do this two times to completely silence the squeak.

The second method is to place a pair of thin washers or shims behind the bracket where it bolts to the axle. You are trying to slightly move the caliper bracket outward just a bit. I think GM actually sells the shim kit for this exact problem, however i dont know the part number.

The reason this happens is normal wear on the axle c-clips and or doing a R&P change. The axle is now allowed to extend outward in a hard turn and the rotor makes the loud squeak when it contacts the caliper bracket.

The areas in yellow (arrows) are where it rubs

 

Awesome.. I was thinking it had to be related to axle wear, I guess my axle is drifting inward during the turn.

 

Please post on the correct forum. LT1 Based Engine Tech is only for questions about engines. I'll move your thread to the "Suspension, Chassis and Brakes" forum.