1. Simple Checks (Do these FIRST):
* Fluid Level and Condition: Check the automatic transmission fluid (ATF) level with the engine running and warmed up. Is it low? Is it dark brown, burnt smelling, or gritty? Low or severely contaminated fluid is a major culprit. If it's low, add the *correct* type of ATF (consult your owner's manual). If it's bad, a complete fluid and filter change is likely needed.
* Selector Lever: Make sure the shift lever is moving freely and engaging all the gears correctly. Sometimes, the linkage can bind or become disconnected. Inspect for any obvious damage or looseness.
* Battery Voltage: A low battery can affect the transmission's electronic controls. Check the battery voltage with a multimeter. A weak battery can cause erratic shifting or no shifting at all.
* Safety Interlocks: Make sure your brake pedal is firmly pressed down. Some vehicles won't shift out of park without the brake pedal pressed. Also, check for any other safety interlocks (like seatbelt indicators) that might be preventing shifting.
2. Intermediate Checks (If simple checks don't work):
* Transmission Solenoids: These electrically controlled valves regulate fluid flow within the transmission. A faulty solenoid can prevent shifting. This usually requires a professional diagnosis with a scan tool to check for diagnostic trouble codes (DTCs).
* Torque Converter: A malfunctioning torque converter can cause slipping or inability to shift. This is a more involved repair, potentially requiring transmission removal.
* Transmission Linkage: Check the linkage connecting the shift lever to the transmission. Make sure it's properly adjusted and not damaged.
* Vacuum Lines: Some older automatic transmissions rely on vacuum lines. Inspect for leaks or damage.
3. Advanced Checks (If intermediate checks fail):
* Diagnostic Trouble Codes (DTCs): A scan tool can read DTCs stored in the transmission control module (TCM). These codes provide valuable clues to the problem. Auto parts stores often offer free code reading services.
* Transmission Valve Body: The valve body contains many internal valves that control fluid flow. A problem here often requires a rebuild or replacement of the transmission valve body.
* Transmission itself: If all else fails, the transmission may require a rebuild or replacement. This is the most expensive option.
Important Considerations:
* Professional Help: If you're not comfortable working on your transmission, it's best to take your car to a qualified mechanic or transmission specialist. Improper diagnosis and repair can lead to further damage.
* Year/Model Specifics: The exact nature of the problem can vary significantly between different years and models of the 1993 Town Car. Referring to a repair manual specific to your vehicle's year and model will be immensely helpful.
* Safety: Never work under a car supported only by a jack. Use jack stands for safety.
Start with the simple checks. If those don't solve the problem, move on to the intermediate and advanced checks, or seek professional help. A proper diagnosis is key to resolving the shifting issue.
