Here are some of the most likely culprits:
* Transmission Problems: This is the most probable cause. The blinking overdrive light points directly to a transmission issue. Possible problems include:
* Low Transmission Fluid: Check your transmission fluid level immediately. Low fluid can cause severe damage. If it's low, you need to find out *why* it's low – a leak is a serious problem.
* Transmission Solenoid Problems: These are electrical components that control the shifting of the transmission. A faulty solenoid can cause erratic shifting, the overdrive light to blink, and unusual noises.
* Torque Converter Issues: The torque converter connects the engine to the transmission. Problems here can lead to slipping, noises, and the overdrive light flashing.
* Worn Clutch Packs or Bands: These components wear down over time and can cause slipping, harsh shifting, and unusual noises.
* Internal Transmission Damage: This could range from worn gears to more serious internal failures. This is usually the worst-case scenario and often requires a costly rebuild or replacement.
* Other Potential Issues (Less Likely, but possible):
* Vehicle Speed Sensor (VSS) Problem: A faulty VSS can interfere with the transmission's ability to shift properly and trigger the overdrive light. The engine noise would be less directly related in this case.
* Transmission Range Sensor: This sensor tells the transmission what gear to be in. A faulty sensor could cause shifting problems.
What to do:
1. Check the Transmission Fluid: This is the first and most important step. Check the level and condition (color, smell). Brown, burnt-smelling fluid is a bad sign.
2. Don't Drive It: Continued driving with a blinking overdrive light and engine noise risks causing further and potentially catastrophic damage to the transmission.
3. Get it Diagnosed: Take your Expedition to a qualified mechanic specializing in transmissions or a reputable repair shop. They can use a scanner to read the transmission's trouble codes, which will help pinpoint the exact problem.
Ignoring the problem will likely lead to a much more expensive repair later. Addressing it promptly is crucial.
