These trannys can have a problem with the shift solendoids sticking if the maintenance hasn't been performed regularily. I have had 100% "luck" with dumping in 1 bottle of "Trans Tune" made by the SeaFoam company. Run the vehicle for 30 minutes on the open road and then drain the fluid and change the filter. I have had 3 of these vans that I did this to and it fixed the problem on all 3.