Home › Forums › Stay Dirty Lounge › Service and Repair Questions Answered Here › EVAP System or Transmission Problem? › Reply To: EVAP System or Transmission Problem? March 27, 2021 at 1:40 pm #989706 Ronald TylorParticipant PURGE VALVE ON GM 3800 AFFECT HARD SHIFTS ON TRANSMISSION mine does this on my 03 Buick lesabre it never shifts hard when the purge valve is not not rattling