I drive a 1981 Toyota Corolla TE72 3tc 4 speed manual transmission, and I think its a T40 transmission. So I am driving home from the store with my wife and as I am shifting through the gears I notice that every time I shift into 3rd, I hear a loud crunch sound. I only hear the noise when shifting into 3rd gear and I only hear it once. Its not a constant sound, but still, I hear it and I swear its getting louder every time. I know I am not the worlds greatest mechanic but I know when its time to pull out the work gloves. My question is, How difficult is it to rebuild a Toyota manual transmission? I consider myself to be a mechanically able person but I have never done this before. I have done engine/transmissions swaps in the past and it was fairly easy but this is a whole new thing for me.
Any Help Is Much Appreciated
This is a picture of when I dropped the trans for the clutch install. Don't know if pictures helps identify trans type for more accurate help.

