my 97 GSR with 78,000 miles on it also does it. When I first got it I couldnt pop it into reverse too well. Sometomes I'd think I'd have it in the reverse gear, then give it a little gas, then slowly let out the clutch, then *GRIIIIIIIIND*. I've done this in my friend's 92 jetta, 94 Geo metro AND 1989 4Runner (the grinding cuz I THOUGHT I was in the reverse gear). I just play with the stick nicely.