Hi so I've got a 3rd to 4th crunch, only happens at high revs. I've heard castrol transmax 75w 90 is really good and helps with the crunch. Anybody used this and offer any options on transmax or maybe something else? Car is 2003 impreza wrx on 124k. Thanks 

Pretty common issue as the syncro's wear. you can try so different oil, but really its only a temporary fix.