The shop so long as you are willing to let it can keep your vehicle as long as needed within reason to correct the problems with the transmission under its warranty unless the written warranty that you presumably have in hand states otherwise.I suggest that you meet with the opwner of the repair facility to set a time table for the return of your vehicle in proper running order. Another option is to consult with an attorney that practices in the area of automotive law and/or make a complaint with your state's bureau of automotive repair.This entity is in charge of fielding consumer complaints with approved automotive repair facilities.