Transmission Related Issues:
* Low Transmission Fluid: This is the first and easiest thing to check. Low fluid can cause all sorts of shifting and power problems, leading to stalling. Check the fluid level and condition. Dirty or burnt fluid is a bad sign.
* Transmission Problems:
* Clutch (if Manual): A worn clutch, pressure plate, or throw-out bearing would cause this. You wouldn't be able to engage gears smoothly or at all in a manual.
* Torque Converter (if Automatic): A failing torque converter in an automatic transmission can cause similar symptoms. It's the component that transfers power from the engine to the transmission. A failing one might lock up intermittently or fail to engage completely.
* Internal Transmission Problems: Worn gears, broken parts, low internal pressure, etc. inside the transmission itself are more serious issues requiring a professional diagnosis and likely a rebuild or replacement.
* Shift Linkage/Solenoids (Automatic): In an automatic, problems with the linkage that connects the shifter to the transmission or failing solenoids can prevent gear selection.
Engine Related Issues (Less Likely but Possible):
* Fuel Delivery Problem: Intermittent fuel pump failure, clogged fuel filter, or issues with the fuel injectors could cause power loss and stalling. However, these usually don't directly prevent gear engagement.
* Ignition System Issues: Problems with the ignition coil, distributor cap, rotor, or wires could cause misfires and stalling. Again, less likely to directly cause the gear engagement problem.
* Crankshaft Position Sensor (CKP Sensor): A failing CKP sensor can cause the engine to stall unexpectedly.
Other Possibilities:
* Neutral Safety Switch: This switch prevents starting the car unless it's in Park (or Neutral). A faulty switch could be interfering with the starting and shifting mechanisms.
Troubleshooting Steps:
1. Check the Transmission Fluid: This is the absolute first thing to do. Check the level and condition of the fluid.
2. Inspect the Shift Linkage (Automatic): Visually inspect the linkage for any damage or looseness.
3. Listen for Unusual Noises: When trying to start and shift, listen carefully for any grinding, whining, or knocking sounds from the transmission.
4. Check Engine Codes (if applicable): A scan tool can read any diagnostic trouble codes stored by the car's computer. This can help pinpoint the problem area.
Recommendation:
Given the symptoms, the transmission is the most likely culprit. Because diagnosing transmission problems requires specialized knowledge and tools, it's strongly recommended to take the car to a qualified mechanic specializing in older vehicles or automatic/manual transmissions for diagnosis and repair. Attempting repairs yourself without the proper expertise could worsen the situation. They can diagnose the specific issue, be it low fluid, a failing component, or major internal damage.
