I don't understand how a worn-out 1st synchro keep you from shifting 4-3? shruggy

Speaking of "on the side of the road wondering": Way back around '85, I had a similar feeling develop in my A-833 about 2 miles from home (at midnight with rain coming, of course). Finally it stuck "between" 3 & 4 and the car wouldn't move at all. Hiked home, drove back with a toolbox, got underneath and moved the shift arm to 4, N, 3... no resistance and the driveshaft stayed locked. Then of course the clouds opened up and within seconds I was lying in an inch of water. Gave up for the night!

Next day had it towed home, pulled the side cover, and found that the neck had snapped off the 3/4 shift fork. Popped in a new fork, back in business.