I have a 06 wrx salvage title with 30,000 on it and im getting a grind into 4th gear when I shift above about 3,000rpms. I have changed the tranny fluid and the oil had no little metal shavings or anything. I was just looking for opinions on the cocktail and if anyone knows where to find the redline lightweight shockproof stuff. i went to autozone and shucks oriely and walmart

and they all didnt have it. is there anything that is a different brand that does the same thing? i also got a different brand instead of Castrol Hypoy C 80w90 it is 80w90 though. is that ok?
let me know, thanks.