Clunking/bang from rear of truck

[Ilovemycressida]

I have this clunking/banging from the back of my 80 when it shifts gears. Probably a noob for asking but I can't find any solutions or reasons why it is doing this. Started a couple days ago.but when my foot is on the gas slightly when it shifts there is less of a banging

 

[Delancy]

U joints.

 

[Ilovemycressida]

U joints.

Thank you very much. Gonna check it out once it dries up and gets sunny since I don't have a garage.