Fluid Related Issues:
* Low Transmission Fluid: This is the most common and easiest to check. Low fluid level can cause shifting problems, leading to incomplete or no gear changes. Check the fluid level with the engine running and warmed up – consult your owner's manual for the proper procedure. Low fluid could also indicate a leak, which needs attention.
* Dirty or Contaminated Transmission Fluid: Old, dirty fluid loses its lubricating and hydraulic properties, affecting the transmission's ability to shift properly. A fluid and filter change is often recommended.
* Incorrect Transmission Fluid: Using the wrong type of transmission fluid can severely damage the transmission. Always use the type specified in your owner's manual.
Mechanical Issues:
* Solenoids: These are electromagnets that control the flow of fluid to shift the gears. A faulty solenoid can prevent a gear change. This often requires a transmission specialist to diagnose.
* Valve Body: The valve body is a complex assembly within the transmission that controls fluid flow. Problems within the valve body can cause shifting issues. This is usually a significant repair.
* Torque Converter: This connects the engine to the transmission. If it's malfunctioning (e.g., slipping or locked up), shifting problems will occur.
* Clutch Packs: Internal wear and tear on the clutch packs can lead to slipping or inability to engage gears. This often requires a transmission rebuild or replacement.
* Shift Linkage (if applicable): On some older vehicles, a mechanical linkage controls shifting. Wear or damage can interfere with proper shifting.
* Transmission Computer/PCM: The Powertrain Control Module (PCM) controls the transmission's electronic functions. A faulty PCM can cause various shifting problems. This usually requires diagnostic testing by a mechanic.
Other Potential Issues:
* Low Engine RPM: If the engine isn't revving high enough, the transmission may not shift into a higher gear.
* Safety Features (e.g., hill assist): Some safety features can temporarily prevent shifting under certain conditions.
Troubleshooting Steps:
1. Check the transmission fluid level and condition: This is the first and easiest step.
2. Check for any error codes: Use an OBD-II scanner to check for diagnostic trouble codes (DTCs). This can point to specific problems.
3. Listen for unusual noises: Grinding, whining, or banging noises coming from the transmission often indicate internal problems.
Important Note: Diagnosing transmission problems can be complex. If you're not experienced with automotive repair, it's best to take your 1999 Ford Taurus to a qualified mechanic or transmission specialist for diagnosis and repair. Attempting repairs yourself without the proper knowledge and tools can cause further damage and increase the cost of repair significantly.
