Is there a warm up mode on the 6 spd. auto transmissions? Mine won't shift past 4th (or maybe its 5th) so at 55mph I'm hitting 2100 rpm's. Also, the engine brake won't engage for the first 5 to 10 minutes I drive depending on the temperature. I've also noticed that the exhaust brake kicks in sporatically during decel when my speed is less than 20 mph and I get some clunking from the drivetrain when it does. Are these normal occurences for these trnny's (along with the noisy shfting into park I experience)?