Archived charging problem

[dodge peck]

I have a 97 3500 its got 212000 miles on it. Recently my volt gauge has been low an it'l be locked in third gear an won't come out. . i can slide the selector to 1 an it'l go to second gear. . an can take a jumper wire from the pos. battery terminal to the bottom little post on the alt. an it'l start charging. . but now it's stating to be come harder to get that to work. . any ideas?? no one seems to b able to help me. i have new batteries an 3 new alts.