Hard shifting

[Litenin]

Wondering about an issue I am having with my 89 with 4.2, manual trans, don't know what transmission it is?
After driving for about 20-30 minutes, I stop at my location for a bit. When I get back in, the transmission is very hard to shift. Any ideas what could be the issue?

 

[Pman]

I would start with the basics. Fluid full? Proper type? You could have a ba10/5 or an ax15. Look at the transmission and see if it looks like it bolts together in halves.