1) Driveline Backlash: This is the most common cause of a clunking noise in the Expedition. When you accelerate or decelerate, there is a slight amount of backlash (or slack) in the driveline. This can cause the components to knock or clunk against each other, creating the noise you hear.
2) Worn CV Joints: The CV (constant velocity) joints in the axles can also wear out and cause a clunking noise. This is more common in vehicles with higher mileage or those driven in harsh conditions. When the CV joints wear out, they can allow the axle to move around more than it should, which can cause the components to knock against each other and make a clunking sound.
3) Loose or Damaged Motor Mounts: The motor mounts hold the engine in place, and if they become loose or damaged, it can cause the engine to move around excessively. This can lead to the engine components knocking against each other and making a clunking noise.
4) Transmission Mount Issues: A clunking noise can also be caused by a worn or damaged transmission mount. The transmission mount is responsible for keeping the transmission in place and preventing it from moving around excessively. If the transmission mount fails, it can allow the transmission to move enough to make contact with other components, resulting in a clunking sound.
5) Incorrect Transmission Fluid Level: Having too much or too little transmission fluid can also cause a clunking or banging sound. If the fluid level is too high, it will foam and aerate, which can cause the transmission to slip and bang. If the fluid level is too low, the gears will not be properly lubricated and can grind or knock against each other.
Recommendation
If you hear a clunking sound on and off the throttle in your Ford Expedition, it's important to take it to a reputable mechanic for diagnosis and repair. While some of the causes of this noise may be minor and inexpensive to fix, others can be more serious and expensive if left unaddressed. By having the issue diagnosed and repaired promptly, you can help to prevent further damage and keep your vehicle safe to drive.
