1. Low transmission fluid: Check the transmission fluid level and add more if necessary.
2. Dirty transmission fluid: Change the transmission fluid and filter if it is dirty or has a burnt smell.
3. Faulty shift solenoids: Shift solenoids control the flow of fluid in the transmission, which changes gears. If a shift solenoid is faulty, it can cause the transmission to shift improperly.
4. Faulty transmission control module (TCM): The TCM is the computer that controls the transmission. If the TCM is faulty, it can send incorrect signals to the shift solenoids and cause the transmission to shift improperly.
5. Mechanical problem in the transmission: There could be a mechanical problem in the transmission, such as a worn clutch or damaged gear. This would require professional diagnosis and repair.
6. Faulty wiring or electrical connections: Check the wiring and electrical connections to the transmission and TCM to make sure there are no loose or damaged wires.
If you are not comfortable performing these checks or repairs yourself, it is best to take your van to a qualified mechanic for diagnosis and repair.
