03 6spd lost 4th, and now 3rd too

[Dallasmn26]

Like the title says last week while driving I went to shift into 4th and it wasn't there! It didn't grind or pop just acts like the truck is in neutral, now third has done the same thing, the shifter feels right but there is nothing there, the tranny doesn't make any noise or act diff in any other gear, is there any roll pins that can fall out or break for just 3-4 shift rail? Is there any inspection port on this thing