I have a 2006 chevy coalt ss with a standard transmission. while im driving it and i shift geareven if i do it slow andi give it gas it acts like the clutch is still engaged and revs the rpms up alittle then will go its like it has a lag to it. im not sure if im looking at a transmission or clutch problem, it is like the tranny is slipping in a way, at the same time i also have problems getting it in reverse sometimes, and you can hear what sounds like a chattering noise when i downshift to slow down. the car has already had a new tranny put in it after 42k it now has 92k on it and im trying to figure out whats wrong before i lose warrenty, since i had the tranny replaced i rarely dog it out, every once in awhile i will but not often. any input would be great

 

Sounds like a clutch to me. I just got a gmpp stage 2 clutch and am very happy with it. heres a link to it and the part number is on the site if you wanted to go to the dealership and order it. Ecotec LSJ Clutch Upgrade Kit 19212712 - Crate Engine Depot
ps this clutch engages at the floor appose to engaging when you are all the way off the clutch which i like a lot better.

 

Clutch gets my vote. probably slipping when you get on it.

 

Heres a good way to tell. If it is hard to shift in all gears its the clutch, if its only hard to shift in a single gear is a syncro which is a tranny problem

another thing is if you floor it and the speedo stays still while the rpms climb its the clutch.
another way to tell if it is a clutch problem is if you are at a stop, put it in 5th and slowing let out the clutch and if the car wants to die then its not a clutch problem, if you feel it slipping badly and the car doesnt want to die then its the clutch.
hope it helps