I had to replace my front rotors last week-end. it was a pain to change the captive rotors. The big nut was a challenge to take off, so I ended up taking a torch to heat up the big nut. I was able to finally do it. Everything seemed to run great for a couple of days, then it started to make this nasty grinding noise that seems to be getting louder.
Q1) How can I tell it's the wheel bearing for sure (seems to be pretty bad on driver side).
Q2) I noticed that if I take the wheel off and put it in neutral, the wheel still spins if I start the motor. I thought it should not spin at all in neutral. is this a bad sign that my tranny is about to go?
Thanks.
Q3) One side of the new disk seems to have some scratches in it, the other side has the mirror finish. I took the caliper off but can't see anything that would have caused the scratching.

 

the bearing is probably fine. sounds like a sticky caliper. im having a similar problem due to a buddy helping me change my pads/rotors. when c clamping the the passenger piston back in he pushed the piston in way too far and now i also have a spongy brake pedal.

maybe this happened to you too? not sure if the seal on the master is blown or if the caliper needs a rebuild

 

well I took the calipers off as well. I forgot to mention something though: When I was banging on the ball joints to pull out the assembly that has the rotors on it, I had the callipers hanging and the piston was pointing down. As I kept banging, I didn't notice that the piston kept moving out and at one point it just fell out, making a big mess there. I took the caliper off and put the piston back with the rubber seal around it and everything and it seemed to work ok. Not sure it's just a sticky caliper, I mean I don't think it would make a grinding noise with brand new pads even if it was sticky.
I did use a c-clamp and pushed the caliper as far as it will go, and it didn't seem to hurt anything.

 

i took the rotor assembly off and sure enough the wheel bearing is busted. I guess my big question is what did I do to mess it up? was it the heat? or the banging? or maybe it was already pretty bad and it just happened to go bad a few days after I did the rotor job? I did notice when I took it off that it wasn't spinning as easily as I thought it should, but it was still moving smoothly.

Another thing was I cleaned the whole thing with brake parts cleaner spray and a little bit got into the bearing. could that have caused the grease to dissintegrate and the bearing to go?

This time when I took it apart, the hub nut was a bit loose, though I don't think there was any play there that would have caused this. I remember tightening it , but I guess I didn't tighten good enough.

 

It was probably the banging that did it.