the car is a 94 z28 m6 with 98,000 on it. about a week ago i got back from a trip after riding about 2 hours in 6th. when i came off the interstate, i went to put it in 5th and i could feel and hear some grinding. not like the kind when you miss a shift. a softer grinding but it did it until i let the clutch out. it did this in every gear but only does it real bad when downshifting. i let the car sit overnight and drove it the next morning. wasnt doing it nearly as bad. only in 1st gear. but now it only does it when im downshifting to first. and it does it in first even after the clutch is out sometimes. i dont know much about transmissions so i have no clue what it could be. any help i would appreciate