* Low Fluid Level (despite recent change): Even with a recent fluid change, there might still be a leak somewhere. Check the fluid level again when the transmission is hot (after driving for a while). A leak could be internal (seal failure) or external (visible leak).
* Internal Transmission Wear: While you didn't find metal shavings, that doesn't rule out significant internal wear. The slipping could be due to worn clutch packs, bands, or other internal components. These components can wear without producing readily visible metal particles.
* Valve Body Issues: The valve body controls fluid flow within the transmission. A problem with the valve body, such as worn solenoids or a faulty pressure regulator, can cause slipping, particularly when the fluid is hot and less viscous.
* Torque Converter Issues: The torque converter is responsible for transferring power from the engine to the transmission. If it's malfunctioning (e.g., due to internal wear or a faulty clutch), slipping can occur, especially under heat.
* Cooler Issues: The transmission cooler (either the radiator-mounted one or a separate cooler) could be partially blocked, causing the fluid to overheat more quickly.
Troubleshooting Steps:
1. Thorough Fluid Level Check (Hot): This is the absolute first step. Incorrect fluid level is a common cause of transmission problems.
2. Check for Leaks: Carefully inspect the transmission pan, lines, and cooler connections for any signs of fluid leaks.
3. Transmission Temperature: If possible, monitor the transmission fluid temperature. A consistently high operating temperature supports the idea of a cooler problem or internal friction. This might require a scan tool capable of reading transmission temperature.
4. Professional Inspection: Given that the problem persists after a fluid and filter change, a professional transmission mechanic should inspect the transmission. They have the tools and expertise to diagnose the internal condition of the transmission and identify the faulty component(s). They might perform a pressure test to assess the hydraulic system's performance.
Ignoring the problem will likely lead to more significant damage and costly repairs. A proper diagnosis by a qualified mechanic is the best course of action.
