I am not familiar with your particular transmission but is it a "top loader" or does it have "levers" on the side. The gm 3-speed transmission can experience the same type of problem. Sometimes this can be from your linkage not being adjusted properly thus allowing you to put one in gear while the other gear is not fully out of gear. I know its a little confusing but def check your linkage adjustments.


Frank
1948 5 Window Chevy 3100 an absolute rescue that is now back on the road
1953 Buick Super 1 family owned since new
1956 3200 Big Window
1985.5 Mustang SVO
1986 Mustang SVO