BP30's with FNSL 4 piston grinding noise?

[jlwdvm]

I have 4-piston FNSL and Spec 37's on the rear of my Firebird track/street car. I had BP10's in all calipers (fronts are Aerolite 6's) for my first track day in May. The brakes performed ok, but I wanted more response for the street and track. I went to a DSE booster and Master cylinder (was a manual Wilwood) and BP30's. I scuffed the rotors with 80 grit before changing pads and bedded them in before my last track day in August. I now love the feel of the brakes, but I'm getting an annoying grinding/rubbing/squeal from the rears. I hear it when I am pulling up to a stop and probably slow to between 5-7 miles an hour. It isn't heard when I am on the brakes....only when coasting. If it starts, I can make it leave by applying the brakes. My rotors had a weird look to them after my last track day and didn't have a uniform burnished look to them. I scuffed the rotors again, but the sound is still there.The sound has been there since I changed pads no matter what I have done. Could it be the pad-rotor interface, of maybe I need to lube some contact points? Thoughts?

[jlwdvm]

Pulled the passenger side wheel last night and started looking around. There is nearly no gap between the pads nad the rotor on either side. However, I noticed a witness mark on my frame rail and started to look around. I have a crushed section of copper line that is basically at the fitting where the hard line meets the SS flex line. It looks like the tab I welded on to the axle tube as well as the copper line itself have contacted the frame when the rear suspension on that side bottomed out. I suspect it is at a section of the track (Autobahn) that is called "The Jump". Luckily no leak and the drivers side is ok, but probably contributing to my problem!

[vette427-sbc]

Pull the pads out, see if they are tapered in any direction? Not a floater rear, so whats your axle end play?