I would start by checking the fluid level and condition.
IF it is low, top with the appropriate fluid. Hopefully the fluid is clean and the filter has been changed at least twice by now.
Lack of maintenance will ruin.
Reading the transmission codes in the computer with the appropriate scanner is the next step if the problem persists. If so post them and we can go further.
Tuesday, August 3rd, 2010 AT 5:37 AM