bought a car two weeks ago. 08 azera 3.8L 180,000. when i first picked up the car within the first two or three days i noticed a hard jerk between swithching through the gears. i know thats not a good sign. Also one day at jack iwas stopped at the drive thru when i let off the brake and didnt move at all. pressed the gas and revd to 2k and jumped foward then back to smooth. i took it to a mechanic and he told me the seller probably replaced all the fluids including the trans which is why i had that problem. Said nothing i can really do. i been driving it the past couple days(4 days maybe 500 miles) kinda harder with no lights on dash and no problems. Also shifting into gears has gotten smoother. a little movment but nothing harsh. Should i plan to replace trans? or buy a new car maybe?