I was driving my S4 TII last night and hear a grinding sound when my boost hit 2psi and up. gets louder as the boost rises. I took off my TID and the shft spins freely and no shaft paly. What can it be? I rev the eng to 8k sitting still and no noise. Only during boost.. thanks.. Stock S4 Turbo installed.

 

endplay?
look for signs of rubbing?

 

Hmm... Ooh... I know. Make sure your turbo/exhaust mani. bolts are tight. They have a tendency to come loose. When they come loose it makes a CRAZY noise. Like a super-fast, vibrating, roaring, purring, knocking noise, lol.

Not sure if that's it, but it's happened to my car a couple times.

 

ok cool.. cold side has no shaft play. will check for back and forth play today to make sure and check downpipe nuts..