Well for one make sure that your adjust ment on the clutch cable is right. you want it to be loose so if you pull up on it you can see it catch. You don't want it so there is constant pressure on the clutch. This will keep the cluch engaged and cause it to grid when shifting. Other wise I would say it is the syncros 2nd gear is well know for this problem. Make sure you change the oil in your tranny too. It might help.