Tools You'll Need:
* U-joint press or suitable alternative: This is the most crucial tool. A press makes the job much easier and safer. Improvised methods exist using sockets and a hammer, but this increases the risk of damage.
* Socket set (metric): You'll need various sizes for the nuts and bolts holding the driveshaft together and the U-joint caps.
* Wrench set (metric): For loosening and tightening bolts and nuts.
* Hammer: May be needed for separating components.
* Punch: To help remove the U-joint straps.
* Grease: To lubricate the new U-joint.
* Torque wrench: Absolutely essential for proper tightening of bolts to prevent premature failure.
* Driveshaft support: To support the weight of the driveshaft while working.
* Safety glasses and gloves: Always wear appropriate safety gear.
* Repair Manual: Specific to your 1990 Chevy 4x4.
Procedure (General Outline):
1. Safety First: Disconnect the battery negative terminal. Support the vehicle securely on jack stands.
2. Locate the U-joint: Identify which U-joint needs replacement (front or rear driveshaft).
3. Drain Transmission/Transfer Case Fluid (if necessary): Depending on the location of the U-joint and how you access it, you may need to drain some transmission or transfer case fluid to avoid spills.
4. Remove the Driveshaft: This usually involves removing bolts holding the driveshaft to the differential and transfer case (or transmission). Use a driveshaft support to keep the driveshaft from dropping and avoid injury.
5. Separate the U-joint: You'll need to carefully remove the retaining straps (clips) that hold the U-joint in place. A punch can help. This is where a U-joint press is invaluable. It carefully presses the old U-joint out without damaging the yoke. Improvised methods risk damaging the yokes, making installation difficult or impossible.
6. Install the New U-joint: Using the press (or your chosen method), carefully press the new U-joint into place. Ensure it's seated correctly and evenly. Grease the U-joint thoroughly.
7. Reinstall the Driveshaft: Carefully align the driveshaft and reinstall the bolts. Tighten to the specifications in your repair manual using a torque wrench.
8. Reattach the Driveshaft: Connect the driveshaft to the differential and the transfer case (or transmission).
9. Check for leaks: Inspect the U-joint and surrounding areas for any leaks.
10. Lower the vehicle: Carefully lower the vehicle from the jack stands.
11. Test drive: Before driving, make sure to check all bolts and connections. Then drive cautiously to make sure everything is working correctly.
Important Considerations:
* Phase the U-joint: Ensure that the U-joint is phased correctly during reinstallation. Incorrect phasing can cause vibrations and premature failure. Your repair manual will explain this.
* Torque Specifications: Use a torque wrench and follow the torque specifications in your repair manual. Over-tightening can damage components; under-tightening can lead to failure.
* Professional Help: If you are not comfortable performing this repair, take your vehicle to a qualified mechanic. The cost of repair is much less than the cost of a damaged driveshaft or other related components from improper installation.
This is a simplified overview. Always consult a repair manual specific to your 1990 Chevy 4x4 before attempting this repair. Improper installation can lead to serious safety hazards.
