* Shift Linkage: Check the mechanical linkage connecting the shift lever to the transmission. It could be bent, broken, or improperly adjusted. Make sure the linkage moves freely and connects correctly to the transmission.
* Transmission Cable (if applicable): Some transmissions use a cable instead of a linkage. Inspect this cable for damage, stretching, or binding.
* Internal Transmission Problems: Unfortunately, the problem could be within the transmission itself. This is more likely if the replacement module didn't resolve the issue. Internal problems could include:
* Broken shift forks: These components move the gears inside the transmission.
* Worn or damaged synchronizers: These help the gears mesh smoothly.
* Low transmission fluid: Check the fluid level and condition. Low fluid or dirty fluid can cause shifting problems.
* Valve body issues (even with a new module): While you replaced the *module*, there might still be other problems within the valve body itself that aren't addressed by just replacing the module. This is less likely but possible.
* Electrical Issues (Beyond the Module): While you've tackled the module, other electrical components could be faulty. This could involve:
* Wiring harness: Check for damaged or corroded wiring related to the transmission.
* Transmission Range Sensor (TRS): This sensor tells the computer the selected gear. A faulty TRS can cause shifting problems.
* PCM (Powertrain Control Module): A malfunctioning PCM can prevent the transmission from shifting correctly. This is less likely but possible.
Troubleshooting Steps:
1. Check Transmission Fluid: This is the easiest and cheapest check. Check the fluid level and condition. If low, add the correct type of fluid. If dirty, a fluid change and filter replacement may help (though it may not solve a mechanical problem).
2. Inspect Shift Linkage/Cable: Visually inspect for damage and check for smooth, free movement.
3. Professional Diagnosis: Given you've already replaced the module, a professional mechanic with experience in transmissions is likely needed. They have diagnostic tools to identify the root cause, which could save you time and money in the long run by avoiding unnecessary parts replacements. They can test for electrical problems and assess the internal health of the transmission.
Don't attempt to diagnose or repair complex transmission problems yourself unless you have significant mechanical experience. Improper repair could lead to further damage.
