Possible causes include:
* Low Transmission Fluid: Check your transmission fluid level immediately. Low fluid can cause overheating and damage, leading to the symptoms you're experiencing. Important: Check the fluid level while the engine is running and warmed up, using the dipstick.
* Transmission Solenoid Problems: These electro-magnetic valves control fluid flow within the transmission. A faulty solenoid can prevent gear shifting and cause the overdrive light to flash.
* Transmission Valve Body Issues: The valve body houses many solenoids and valves; a problem here is a common cause of transmission failure in the Windstar.
* Torque Converter Failure: The torque converter transfers power from the engine to the transmission. Failure can lead to a complete loss of drive.
* Internal Transmission Damage: This could be anything from worn clutches and bands to a broken planetary gear. This is likely the most serious scenario, usually requiring a rebuild or replacement.
* Wiring or Electrical Problem: Although less likely given the complete loss of function, a short circuit or faulty wiring to the transmission control module (TCM) could be causing the issue.
What you should NOT do:
* Keep trying to drive it: Further stressing the transmission will likely cause more damage.
What you SHOULD do:
1. Check the transmission fluid level (as described above). If it's low, it's a potential emergency, but it won't fix a broken transmission.
2. Have it towed to a qualified mechanic or transmission specialist. Attempting DIY repairs on an automatic transmission is generally not recommended unless you have significant experience.
3. Describe the symptoms to the mechanic precisely. The flashing overdrive light and complete loss of drive/reverse are crucial pieces of information.
It's highly unlikely you can fix this yourself. The cost of repair will depend heavily on the nature of the problem. A low fluid level (and the resulting damage) might be relatively inexpensive to fix, while internal transmission damage could be very costly. Get a professional diagnosis to understand the extent of the problem and the repair options.
