SM465 wont shift?

[Orangette]

Need some help, i am at a loss.

I have been driving my '78 K20 for about 2 months now, no issues at all, I have driven plenty of standard trucks and i dont ride the clutch.

except since the other day it started acting up

If i depress the clutch at a standstill the clutch acts like it should and i can put the trans into any gear (I always start in 2nd)

But once i get moving, the truck wont let me get out of gear without rev-matching, when i depress the clutch pedal it acts as it should, just the trans wont pop out of gear without rev matching, same goes with trying to pop it into gear, i have to rev match!

The weird thing is I have zero problems getting the truck to move, it moves no problem, i can stop at the stop light with the clutch in no problem.

I have adjusted the clutch linkage and it hasnt changed it at all

Any help?

[mud.man.rj]

Sounds like the pressure plate is getting weak, releases but not quite enough.

[tucsonjwt]

For me, this was the adjustment nut on the clutch linkage. It should show about 1" of thread when adjusted properly. I would tighten that linkage first.
You can tighten it almost all the way to make sure it works, then back it off to where you like the feel of the clutch. My linkage was missing the wave washer and it loosened up. I suppose you could also double nut the thread to keep it set.