Hi Larry,
I had the same problem with my 49 3100 spd. It happened "occassionally" but occurred more frequently as time went on. I could sometimes fix it the same way you do (trying not to get grease on my work shirt!), but sometimes it was "stuck" further down the shift linkage. Pulling up on the linkage from the transmission sometimes worked, but I've driven home stuck in third gear twice!
After thinking about it quite a bit, my final solution was to buy a t-5 transmission and the rear end from a 59 1/2 ton. I'm pulling the old rear end off this weekend.
Dave
