Car will not go into reverse gear - Help

I have a '77 930 w/4 speed trans. I can not seem to find the reverse gear. The usual 'spring resistence' I normally would feel when moving the shift lever to the left and forward does not seem to be there. It is like I have lost the reverse shift position completely. I am goning to try to remove
shift cover and take a look. Any suggestions on what I should be looking for.
When it was working I never had any problems with any of the gears. I am hoping it is just a linkage type of problem. Any help will be greatly appreciated.

Thanks.

sounds like a worn out bushing problem. the shift coupler bushings just break and fall out. easy to see.