* Driveshaft U-joints: Worn or damaged U-joints in the driveshaft are a common culprit. At certain speeds, the worn joints will create vibrations that translate into bucking and shuddering. This is especially likely given the age of the vehicle.
* Transmission issues: Problems within the transmission, such as low transmission fluid, worn synchronizers, or internal damage, can cause shuddering, particularly under load at specific speeds.
* Differential issues: Similar to transmission problems, issues within the rear differential (worn bearings, damaged gears, low fluid) can create vibrations that manifest as bucking and shuddering.
* Tires: Uneven tire wear, improperly balanced tires, or tires with different tread depths can cause vibrations that become more pronounced at higher speeds. Check for cupping or feathering on your tires.
* Wheel bearings: Worn wheel bearings can also contribute to vibrations. Check for play in the wheels.
* Torque converter (automatic transmission): A failing torque converter can cause shuddering, especially during acceleration and at specific speeds. This is more likely if you have an automatic transmission.
* Balance shaft: The 3.4L V6 engine in your Tacoma has balance shafts. If there is an issue with these, it could lead to vibrations that are felt at certain engine speeds, which would translate to the shuddering you describe.
Troubleshooting Steps:
1. Check tire pressure and condition: Inflate tires to the recommended pressure and inspect for uneven wear, damage, or mismatched tires. Consider rotating them.
2. Inspect driveshaft: Look for any obvious damage to the driveshaft, U-joints, or CV joints. Listen for clicking or clunking noises while driving.
3. Check fluid levels: Check the transmission fluid and rear differential fluid levels. Low fluid can cause problems.
4. Have a professional inspect: Because several components could be the cause, a mechanic should inspect the vehicle thoroughly. They can diagnose the issue more accurately through a test drive and inspection of the drivetrain components. They may need to conduct road tests at the specific speed range where the problem occurs.
Don't ignore this issue. Continuing to drive with a bucking and shuddering vehicle can cause further damage and potentially lead to a more serious and costly repair.
