I recently purchased a used 2008 Ford Ranger. Not long afterwards I began having trouble getting it into gear. I took it in and the clutch was worn out and needed to be replaced. The slave and master cylinder were replaced as well. I now have a new clutch that works well most of the time but sporadically the clutch stops working and I either have great difficulty shifting gears or cannot get it into gears at all. This can last for five minutes or a whole day of driving. Then it goes back to shifting well. I've brought it back to the mechanic numerous times and he cannot find anything wrong with it. I am hoping someone may have some insight into this problem.