Have a 1990 manual transmission with 300 engine. Started getting hard to go in all gears at all speeds. I pulled the shifter out of the transmission to see what was going on. Heard a pop, and now transmission won't shift at all. First time into a transmssion. I could use some help with cause of rough gear change and what do I do to get shifter back in and functioning. 180K on mileage. Thanks to anyone who can help.