2004 lancer ralliart. When I let the clutch out and it goes into gear i where a rattling sound that goes away after a second. I have also heard a loud pop if i try to downshift to slow down or sometimes when i take off. The suspension is pretty new and is suppose to have a 2 month old stage 3 exedy clutch so i'm not sure what the problem is.
edit: I no longer have this car, but it turns out it was the throwout bearing was coming apart and in turn messed up the synchros due to not relearn completely.

 

input shaft bearing...that's my guess