There is a seal in the top half but not really a bushing...
There is also a ball, spring and socket bolt on the detent that may be too tight (front of case)
If loosening the detent ball and a little squirt of PB Blast/WD40 doesn't free it up, you may have internal problems...
Pull the bolts around the case, split it (put the bolt back in the shaft and "tap" it out of case) and check out the internals, shift keys etc...