I found an old transmission in the barn that had a tag on it that said broke. but when I took it apart at the back where the driveshaft goes in I noticed it didn't have a U joint inside the cover/housing and the one I took out of the truck has a broken U joint in the back so I'm not sure which transmission is the correct one for this truck
Do you have a picture of the u-joint? Do you simply just need a replacement u-joint to fix your current transmission?