* Steering Dampener: This is the most likely suspect. A worn or faulty steering damper (shock absorber for the steering system) won't control the steering wheel's reaction to bumps, leading to violent shaking. A 6-inch lift and larger tires exacerbate the need for a properly functioning damper.
* Wheel Bearings: Worn wheel bearings can cause a vibration, especially under load (braking or hitting bumps). They'll often make a growling or humming noise too.
* Balance and Alignment: With the lift and larger tires, it's crucial that the wheels are properly balanced and aligned. An imbalance will cause shaking, particularly at higher speeds, but can also contribute to vibrations at lower speeds when hitting bumps. Incorrect alignment will affect how the tires interact with the road, causing instability and shaking. This needs to be done *after* the lift installation.
* U-joints (Driveshaft): Worn U-joints in the front driveshaft (if applicable to your Z71's drivetrain) can cause vibrations that are felt most intensely during acceleration and deceleration, and can worsen with bumps.
* Axle Shafts/CV Joints (If applicable): Worn CV joints (if your front axle uses them) can cause similar symptoms to U-joint problems, particularly when turning or accelerating/decelerating over bumps.
* Control Arm Bushings: Worn control arm bushings can lead to excessive movement and play in the suspension, resulting in shaking and instability. The lift kit itself may have stressed these bushings, leading to premature wear.
* Improper Lift Kit Installation: An improperly installed lift kit is a significant possibility. Incorrect geometry or loose components can cause many of the symptoms described. Double-check *all* bolts and connections in the suspension system. Incorrect caster or camber angles due to improper installation can cause vibrations, particularly on bumps.
* Bent Parts: Impact damage from hitting a pothole or other obstacle could have bent a component (control arm, axle, etc.) even if it wasn't immediately obvious.
Troubleshooting Steps:
1. Inspect the steering damper: This is the easiest and cheapest initial check. Look for leaks, damage, or excessive play. Replace it if necessary.
2. Check wheel bearings: Listen for noises (growling, humming) when driving and have a mechanic inspect the bearings for play.
3. Have the wheels balanced and aligned: This is essential after any significant suspension modification.
4. Inspect U-joints and CV joints (if applicable): Look for excessive play or damage.
5. Thoroughly inspect all suspension components: Look for any signs of wear, damage, or looseness. Pay close attention to the bushings.
6. Re-check the lift kit installation: Make sure everything is properly tightened and installed according to the instructions.
If you've checked these and the problem persists, it's best to take it to a qualified mechanic specializing in lifted trucks. They have the experience and equipment to diagnose and fix the issue properly. Remember to mention all the work already done to avoid repeating unnecessary checks.
