03-04 neon transmission problems

Hey guys, I'm currently working on a 2003 dodge neon sxt. my buddy brought it to me with a "bad tranny". From experience i have had transmissions that the "D" gear blew and it worked only in the "1, 2, and R". Now im trying to find out if his complete tranny is blown or if its a cable. Do the trannies have cables? is there a linkage on here that could have gone bad? He was driving on the highway when it went out. It slowed down and was as if it was in neutral. After it sat for 2 hours while i went and got my trailer, it worked for a brief moment when i was getting it on my trailer.. The fluid is full, and i'm completely stumped. HELP ME!!!