Just wanted to update this thread after my mechanic looked at it this weekend when I was having him change my transmission fluid. He believes the issue has something to do with he brakes, either the caliper is sticking or the new rotors I have are not true. Couple reasons for this after he took it for a test drive; it seems the issue gets worse the more you drive it (vibration is not as bad when it's cold), he also noted that if you press the brake firmly the vibration isn't as bad, and after inspecting the rotors, the driver's rotor on the inside looked to have uneven wear (I'll try to take a picture and post it).

Now I have just replaced the rotors with Stoptech cross drilled (normally would have just gotten blanks but the PO had cross drilled ones, and my rears appeared ok so I just matched the front). Also replaced the pads with EBC red stuff. Before I was getting bad vibration under hard braking typical of a warped rotor. That has gone away. Also, I didn't fell like the pistons were seized when I pushed then in with a c clamp and metal plate to make room for the new pads, but I guess that doesn't mean they still aren't sticking. I had vibration issues before I changed out all these parts (engine bracket, motor mounts, axles), but I the more I think about it, this vibration is different than it was before, so maybe the caliper is sticking more now with the new rotors and pads (or possibly the rotors are faulty).

After searching on here last night, I did buy an IR thermometer on Amazon last night and when it comes in I will go drive it and check the temp and see if one rotor is getting hotter than the other.

I know you can rebuild the calipers, but has anyone had luck with the calipers from BavAuto? That's the only place I could find calipers for the 4.8is and the price is very good. BMW Parts and BMW Accessories | Bavarian Autosport


I still will probably change my thrust arms for good measure.