Here's a breakdown of troubleshooting and potential fixes, progressing from easiest to most involved:
1. The Obvious Checks:
* Shift Linkage: Carefully inspect the linkage connecting the shifter to the transmission. Look for any broken or bent components, loose bolts, or binding points. Wiggling the linkage gently might free a stuck component. A spray lubricant (like WD-40, followed by a dry lubricant like silicone spray) can help if there's friction. Be cautious not to overspray and damage electrical components.
* Parking Brake: Ensure the parking brake is fully released. A partially engaged parking brake can sometimes interfere with the shifter.
* Clutch (if manual): If it's a manual transmission, make sure the clutch pedal is fully depressed when trying to shift.
* Transmission Fluid: Low or contaminated transmission fluid can cause shifting problems. Check the fluid level (consult your owner's manual for the location and procedure) and its condition. If it's low, add the correct type of fluid. If it's dirty or burned, a fluid change is necessary.
2. Intermediate Steps:
* Battery Disconnect: Disconnect the negative battery terminal for a few minutes. This can sometimes reset the electronic components that might be contributing to the problem.
* Start and Rock the Vehicle (Manual): If you have a manual transmission, try starting the engine and gently rocking the car back and forth while trying to shift. This can sometimes free a stuck gear.
3. More Involved Issues (Likely requiring professional help):
* Shift Cable Adjustment: The shift cables might need adjustment. This is a more advanced repair and requires a good understanding of your vehicle's transmission system. Incorrect adjustment can cause further damage.
* Internal Transmission Problems: The most serious cause is a problem within the transmission itself, such as a broken shift fork, worn synchronizers (manual transmission), or other internal damage. This often requires professional diagnosis and repair, likely involving a significant expense.
* Electrical Issues: On some models, electronic components control the shifting mechanism. A fault in the electronic control system might be the culprit. Diagnosing this requires specialized tools and expertise.
When to Call a Professional:
If the above steps don't resolve the issue, it's crucial to consult a qualified mechanic. Attempting further repairs without proper knowledge could cause significant damage to your transmission, leading to costly repairs. A mechanic can properly diagnose the problem and perform the necessary repairs safely.
Important Note: A 1999 Ford Explorer is relatively old. Before undertaking any repairs, consult a repair manual specific to your year and model. This will provide detailed diagrams and instructions. Using the wrong type of fluid or attempting incorrect adjustments can worsen the situation.
