got an 82 4 speed manual that wont allow to shift into fourth gear it grinds when trying to put in in at speed. at idle i put it in gear let off the clutch and it pops out is it the sychonizer or do i need a new transmission

 

Check the shifter seat and bushing, if there bad that will make it hard to shift. Marlin crawler sells a replacement shifter seat and bushing that`s better quality than stock.

 

thanks for the info