Countershaft is internal. You have to disassemble the tranny to inspect everything whats still ok, and what needs to be replaced when rebuilding it. Countershaft must of had excessive wear along with bearings.
Okay backstory: I have a 1996 single cab SX v6 manual truck with over 300k on it. Drive fine when I picked it up but when I drove home on long steeper...
Afaik itsthe throwout bearing, sounds just like it did before it was replaced
The chatter went away whilst slightly tapping my finger on the clutch pedal
Probably clapped out clutch pedal linkage squeaking away. You have more complaints than I've come across in my lifetime.
Have you considered a lobotomy procedure?