* Low Transmission Fluid: This is the first and easiest thing to check. Low fluid level indicates a leak, which needs immediate attention to prevent catastrophic transmission failure. Low fluid also leads to poor lubrication, causing the symptoms you're experiencing. Check the fluid level with the engine running and at operating temperature. Also, inspect the fluid for color and smell; burnt, dark fluid is a bad sign.
* Contaminated Transmission Fluid: Even if the fluid level is okay, contaminated fluid (burnt, dirty) can't lubricate properly and will cause harsh shifting and slipping. A transmission fluid change and filter replacement are necessary if the fluid is contaminated.
* Worn Transmission Clutches or Bands: The internal components of the transmission, such as the clutches and bands, wear out over time. Worn clutches cause slipping, while worn bands lead to harsh shifts and potential slippage. This usually requires a transmission rebuild or replacement.
* Solenoids or Valve Body Issues: The transmission's valve body controls fluid flow to the clutches and bands. Faulty solenoids or a worn valve body can cause erratic shifting, slipping, and stalling. This often requires a valve body rebuild or replacement.
* Torque Converter Problems: The torque converter connects the engine to the transmission. A faulty torque converter can cause slipping, especially during acceleration from a stop. It may need to be replaced.
* Internal Transmission Damage: More severe damage inside the transmission, such as broken gears or bearings, could be the cause. This almost certainly requires a rebuild or replacement.
* Idle Air Control (IAC) Valve: While mostly related to the engine, a malfunctioning IAC valve can cause low idle and stalling, which can indirectly affect transmission behavior when starting and stopping.
What to do:
1. Check the transmission fluid level and condition. This is the absolute first step. If it's low or contaminated, address that immediately.
2. Get a professional diagnosis: Take your car to a reputable mechanic specializing in automatic transmissions. They can properly diagnose the problem using specialized tools and equipment. Don't just start replacing parts hoping to fix the problem, as this can be costly and ineffective.
3. Prepare for potential expense: Transmission repairs can be expensive, ranging from a relatively inexpensive fluid change to a costly rebuild or replacement.
Ignoring the problem will likely lead to more extensive and costly damage. Get it checked out as soon as possible.
