Merlinmagic07

On my Grandfathers jeep he just had the Trans Replaced compleatly by the Jeep dealer last week has only been driven 200 miles since the replacement. and now when it startss its fine and then after you drive it for a few mins when you come to a stop it dies. the best discription i can say is its as if its a manual transmission and you go into gear and just POP the clutch. it lurches and dies. thats what his AUTOmattic trans is doing acting like you are poping a clutch... or something. what could be casueing this to happen?

thanks for any and all help yall can give.