GMC Repair: 1979 chevy transmission ( turbo 350 ), vac line, turbo 350

Question
I put this transmission in about three months ago,and now it wants to slip real bad between a dead stop through second gear. when it does grab it sounds like something is not meshing together.  It also has a vibration when it does grab. need info please.

Answer
hello brandon
this sounds like you should first check the vac line on the tranny moduiale valve other wise this tranny is going out . it also could be pump or tourk converter . was this tranny used when you installed it? if not return it and they will fix it pete