New M22 - 4th Gear Grinds
I recently purchased an M22 to replace an original M20 in my 1967 GTO. It shifts fine under normal driving conditions, however, when I get on it and am going through the gears quickly (taking it to red line), I noticed that 4th gear grinds a little and after it goes into gear, it makes a high pitched winding noise almost like something is still spinning extremely fast. It is only this gear that this occurs in and only happens when I get on it.
I intend to contact the guy I bought it from (it does have a warranty), but would like to hear from others about possible causes. I don't think it is my clutch, otherwise all gears would grind, possibly a synchro? If so, why only at high RPM's?