I have a 91 240sx with 135k and for the past two months when I shift from 2nd to 3rd when going fast it grinds. It still goes in but it grinds 8 out 10 times, also after I drive for a while first gear is usually hard to get into i have to force it most of the time. Wondering if it could just be oil or something small my clutch is fine.

 

try changing the gear oil, if that don't have no effect your tranny may be on its way out

 

If you live where it is cold, that usually will cause it, too

 

Yea cold weather can do it. Change to redline oil. I did and it worked fine. And also you might want to stop going straight into 3rd gear. When shifting outta 2nd hold it in N for a split sec and ease into 3rd. I had the same prob and I never grinded again after doing the technique. i even learned how to do it fast. But then I used redline and never had the prob again.