1. Check the Transmission Fluid:
* Level: This is the most crucial first step. Low transmission fluid is a major cause of harsh shifting. Check the fluid level with the engine running and warmed up (according to your owner's manual). The fluid should be within the specified range on the dipstick. If it's low, add the correct type of transmission fluid (consult your owner's manual). Don't overfill!
* Condition: While checking the level, also examine the fluid's condition. It should be bright red or pink (depending on the original color). If it's dark brown, burnt, or smells burnt, it needs to be changed, and you may have more serious transmission problems. A dirty fluid indicates wear and debris in the system.
2. Check the Battery and Cables:
A weak battery or corroded battery cables can cause erratic electrical signals to the transmission control module (TCM), leading to hard shifting. Inspect the cables for corrosion and clean them if necessary. If the battery is weak, consider getting it tested.
3. Check the Throttle Position Sensor (TPS):
The TPS tells the computer the throttle's position. A faulty TPS can disrupt the transmission's shifting patterns. This usually requires a scan tool to check, and replacing it is relatively inexpensive.
4. Consider the Transmission Filter and Fluid Change:
If the fluid is dirty or the car has high mileage, a complete transmission fluid and filter change is a good idea. This is a preventative measure and can improve shifting, but it won't fix a major internal transmission problem. If you do this, use the correct transmission fluid type specified in your owner's manual.
5. Scan for Diagnostic Trouble Codes (DTCs):
A scan tool (available at auto parts stores or from mechanics) can read diagnostic trouble codes stored by the car's computer. These codes can pinpoint potential problems with various sensors and components related to the transmission. This is vital in diagnosing the issue effectively.
6. Possible Internal Transmission Problems:
If the above steps don't resolve the hard shifting, you may be facing more serious internal transmission issues. This could include:
* Worn clutches or bands: These internal components wear out over time and can cause harsh shifting.
* Solenoid problems: The solenoids control fluid flow within the transmission. A faulty solenoid can cause shifting problems.
* Valve body issues: The valve body controls the transmission's hydraulic system. Problems here can be complex and expensive to repair.
* Low fluid pressure: A pump problem or other internal leaks can cause low fluid pressure, leading to harsh shifting.
What to do next:
* If the fluid is low and/or dirty: Add the correct fluid (if low) and plan for a complete fluid and filter change as soon as possible.
* If you find DTCs: Research the codes online or consult a repair manual to understand their meaning.
* If the problem persists after basic checks: Take your car to a qualified mechanic specializing in automatic transmissions for diagnosis and repair. Ignoring a hard-shifting transmission can lead to more extensive (and expensive) damage.
Important Note: A 1999 Chevy Malibu is an older vehicle. The cost of repairing a major transmission problem might outweigh the car's value. Get a professional diagnosis before committing to expensive repairs.
