83 240D I can't downshift from 4 to 3, however I can shift from 3 to 4
 

I can shift from 3rd gear to 4th gear; however I cant downshift from 4th gear to 3rd gear when I need more power. When I make the downshift, i hear a funny sound and third gear doesnt engage. I tried adjusting the shift linkage, to no avail. I have heard that these transmissions are indestructible so is this one saveable or dead. I spent all summer underneath this car and I am starting to give up. This transmission may be the thing that makes me....

83 240D I can't downshift from 4 to 3, however I can shift from 3 to 4