* Wheel Bearings: This is the most likely culprit. Worn wheel bearings produce a whining sound that often increases with speed. They'll also usually show play or roughness when you try to move the wheel up and down or side to side. This requires replacement, not just bearings. Often the entire hub assembly is replaced.
* Differential Bearings: The differential is inside the rear axle housing. Worn bearings inside the differential can also create a whine, often changing pitch with speed or turning. This is a more serious repair requiring specialized tools and knowledge.
* Axle Shafts: While less common, a damaged or worn axle shaft could contribute to a whining noise.
* Rear Drive Shaft U-Joints: If the noise is more of a rhythmic "clunk-whine," worn universal joints in the driveshaft could be the source.
Before you buy anything:
1. Check the wheel bearings first: Jack up the rear of the vehicle securely (use jack stands!), grab each wheel at the 3 and 9 o'clock positions, and try to move it up and down and side to side. Significant play or roughness strongly suggests a bad wheel bearing.
2. Listen carefully: Does the whine change pitch with speed? Does it change when turning? Does it change depending on whether you're accelerating or decelerating? This information can help pinpoint the source.
3. Inspect the axle boots (if visible): Tears or damage to the axle boots indicate a potential problem that could eventually lead to bearing failure.
Do NOT attempt to drive the vehicle extensively if you suspect a significant problem with the rear axle. Continuing to drive with a bad bearing can lead to catastrophic failure, potentially causing an accident.
In short: While wheel bearings are a likely cause, a proper diagnosis requires a more thorough inspection. Taking your Aerostar to a qualified mechanic for a diagnosis is the best way to determine the exact source of the whine and ensure the correct repair is made. Buying parts without a proper diagnosis could waste your money.
