i have a question about my tranny. when im driving at about 4k and i shift into 4th gear i hear a noise its not a grinding noise but like it rubing or something not catching but it only happens after 4k never below that. can anyone help me out

 

Synchro going out would be my guess, maybe a shift fork, but probably not because all the b-series shift forks I've seen are made of steel.

 

do you know how much it might cost to get fixed or atleast how much the syncro cost