Rough and Loud Ride

My BART ride has been pretty damn good for the past couple of months, but..... Looks like the screeching metal on metal sound is back when going through the tube. However, the ride is also a hell of a lot rougher now. Seriously feels like I am on the Indiana Jones ride at Disneyland. What's the deal?

The Trans Bay Tube is
The Trans Bay Tube is generally loud...all the time. I cannot remember a time going through it where I thought, "hey this is nice" because the noise can get ear piercing. The noise might be from rail wear or the wheels on the train. The rails might need to grind sections of the rail in the tube too.
the tube was actually pretty
the tube was actually pretty pleasant for a while. by pleasant i mean it lost the sound of screeching demons escaping the pits of hell. that sounds is now back. arg.