Get the car scanned. Is (Gear Fault ) appearing on center display. If so you will find that the gear select solenoid is faulty There are two solenoids sometime one will go before the other once one is bad change both. Both solenoids are the same. If solenoids needs changing it is a big job and requires about 2-3qts oil 2 solenoids and a valve cover gasket
Big B
October 2010