I have installed new gears in a couple of transfer cases with no problems.  The one I am work on now I can't seem to get the speedo gear out.  I have run out of ideas to try.  Any suggestions?
Samcan

Samurai, I assume?
Try to get a pair of vice grips on the speedo "bullet" and twist it, to get it loosened up and pull it out.  You could also try a sharp chisel and tap along the outer lip of the bullet to get it to turn (it will likely gouge the edge a little).
Also soak it with penetrant (wd40, pb blaster, etc.) for awhile, that sometimes helps.
As a last resort, you can try heating it a little....but be very careful....since the tcase is aluminum too much heat will ruin it instantly.

I have tried vise grips, WD 40  and a little heat with a propane torch. I use a brass drift to tap all the way around the gear insert in hopes that would free it up.   Have not resorted to the hammer a chisel yet, but I guess that may be next.
Thanks,
Samcan