* Driveshaft U-joints: Worn or damaged U-joints in the driveshaft are a prime suspect. Under acceleration, the increased torque puts stress on the joints. If they're worn, this can cause vibrations that manifest as a wobble, particularly in that speed range. The vibration disappears when you let off the accelerator because the stress is reduced.
* Axle U-joints (half shafts): Similar to the driveshaft U-joints, worn U-joints in the axle shafts (half shafts) can cause vibrations under acceleration. These are less likely to cause a noticeable "wobble" but more of a general vibration, but it's possible depending on the severity of the wear.
* Wheel bearings: While less likely to be the *sole* cause of a speed-specific wobble *only* under acceleration, severely worn wheel bearings *could* contribute. They might create a vibration that's amplified under load. However, you'd likely notice other symptoms like noise or play in the wheels even when not accelerating.
* Transmission issues: Problems within the transmission itself, though less common, could cause vibrations that are felt more strongly under acceleration. This is less likely to be a *wobble*, but more a general shaking or shudder.
* Tire balance or condition: While less probable given the speed-specific nature and connection to acceleration, severely unbalanced tires or tires with significant wear could contribute. However, this would likely be felt at various speeds and not just under acceleration.
Troubleshooting Steps:
1. Visual Inspection: Carefully inspect the driveshafts and axles for any obvious signs of damage, leaks, or excessive play in the U-joints.
2. Listen for Noise: Pay close attention to any unusual noises coming from the front end while driving, especially under acceleration. Grinding, clicking, or clunking sounds could pinpoint a worn joint.
3. Test Drive with an Experienced Mechanic (if possible): Having a mechanic ride along during the wobble can help pinpoint the source of the vibration.
4. Professional Diagnosis: Ultimately, a professional mechanic with experience working on older vehicles is the best resource. They can perform a thorough inspection, including checking for play in the U-joints, inspecting the wheel bearings, and evaluating the transmission.
Important Note: Ignoring this problem could lead to more significant damage and potential safety hazards. It's crucial to address this issue promptly.
