3-on-the-Tree Shifter Adjustment

[Corsair]

So my shifter doesn't like to stay in 2nd gear. Under load especially, the shifter arm will just fall out of 2nd gear into neutral. This is annoying. Any suggestions on what to look for and adjust/replace. Is this an issue within the transmission? I have replaced the rubber bushings that go in the tranny shifters arms that come out the side of the tranny; the ones the shifter arms rest within, the bushings don't fit great since they were for some other application, but it was all I could find.

[nutz]

could be an engine mount
or a worn shift fork/or bearing in the trans
can hold it in gear