I have not touched a manual transmission for many years, but on the 4
speed
Chrysler A-833 that I worked on, there were two shift *forks.* One
would
shift between first and second, and the other between third and fourth.

Fourth, actually connected the main shaft with the input shaft, so that
it didn't use the countergear.

I am guessing that either the fork or the gear clusters that it slides
along the shaft
splines is binding for some reason. Reverse and fifth are most likely
on their own shafts, so that is probably why their okay.

Is there an inspection plate that can be removed to check for proper
operations?

With the mileage that is on the box, it is possible that some of the
bearings are worn.
If you *double clutch* is shifting any easier? If so, the brass
sychronization rings
could be worn. If many of the parts in the box are worn, and you don't
wish to
pay for a rebuild, you may be able to find a lower-mileaged used box at
a salvage
yard.

I would suggest locating a factory service manual that covers that
transmission should
you decide to repair it yourself.

-KM