1. Transmission Fluid:
* Low Fluid: This is the *first* thing to check. Low transmission fluid can cause all sorts of shifting problems. Check the fluid level with the engine running (warm is best, but not overheating) and using the correct dipstick. If it's low, add the correct type of automatic transmission fluid (ATF) specified in your owner's manual. Don't overfill. Low fluid could indicate a leak, which needs addressing.
* Dirty or Contaminated Fluid: Old, dirty, or burnt transmission fluid can prevent proper shifting. A fluid and filter change might resolve the issue. The color and smell of the fluid are good indicators – dark brown or burnt smelling fluid is a bad sign.
2. Electrical Issues:
* Transmission Control Module (TCM): The TCM is the "brain" of the transmission. A faulty TCM can cause a wide range of shifting problems, including complete failure to shift. Diagnosis usually requires a professional scan tool to read trouble codes.
* Shift Solenoids: These are electrically controlled valves within the transmission that direct fluid flow. A faulty solenoid can prevent gears from engaging. Again, a scan tool is helpful for diagnosis.
* Wiring Harness: Damaged or corroded wiring between the TCM and the transmission can disrupt the electrical signals. Inspect the wiring harness for any signs of damage.
3. Mechanical Issues:
* Low Transmission Pressure: This could be due to a variety of issues, including worn-out internal components within the transmission (such as clutches, bands, or planetary gears). This is a more serious problem requiring professional diagnosis and likely a rebuild or replacement.
* Valve Body Problems: The valve body regulates fluid flow within the transmission. Internal problems within the valve body can cause shifting issues. This often requires professional attention.
* Torque Converter: The torque converter connects the engine to the transmission. A faulty torque converter can prevent proper shifting.
4. Linkage Problems (Less Likely on an Automatic):
While less common on automatics, a problem with the shift linkage (if it's a manual transmission – which is unlikely on a 1996 Sebring JXi convertible) could prevent shifting.
Troubleshooting Steps:
1. Check the Transmission Fluid: This is the easiest and cheapest step. Do this FIRST.
2. Check for Trouble Codes: A scan tool can retrieve diagnostic trouble codes (DTCs) from the TCM, providing valuable clues. Auto parts stores often offer free code reading services.
3. Visual Inspection: Inspect the transmission for any obvious leaks or damage.
4. Professional Diagnosis: If you're not comfortable working on your car's transmission, take it to a qualified mechanic. Transmission repairs can be expensive, and a proper diagnosis is crucial to avoid unnecessary work.
Important Note: Driving a car with transmission problems can cause further damage. If your Sebring won't shift, avoid driving it unless absolutely necessary and only for short distances to get it to a mechanic. Towing is usually the safest option.
