I'm having a strange problem with my car.. '96 LT1 M6 with 94k. This just started happening, whenever I let off the gas (only when its in gear) I hear a squeak. I don't hear it when its idling or when its in neutral, and whenever I hit the gas it immediately goes away. My transmission needs to be rebuilt, so I really hope this is a tranny problem and not an engine problem. My oil pressure reads as it always has, no dropping or anything.

Possibly offtopic, but my car also squeaks alittlebit when I shut it off (while its off). Is this normal?

 

Vacuum leak somewhere.