So I got it all apart. As I pulled the left case half off of the right (with the engine laying on the right side) the shift drum fell down due to having the shift mechanism removed from the left side. So this erased any possible evidence if one of the shift forks wasn't engaged on the drum. I put the case halves back together after making sure that the forks and shift drum were all aligned properly. I tried shifting it and turning the trans input by hand... it still misbehaved. I noticed that the double bump on the star wheel that holds the shift drum in neutral wasn't hitting the stopper arm when in neutral. If I shifted down as many times as it would go (supposedly to 1st), the double bump was about 2 or 3 notches away. Removing the drum center confirmed my ultimate mistake. Somehow the index pin didn't hit the groove in the drum center and the shift drum was simply getting indexed in the wrong spots.
Bottom line, I could have fixed this without even taking the motor out of the machine. Oh well. I just need to put the top-end back on and then the motor will be good to go.
- Frank
1984 200ES Big Red
1985 350X (x2)
1986 350X
1986 250SX
1984 Auto-X
1984 ATC70
1985 ATC70