Safety First!
* Support the vehicle securely: Use jack stands, never rely solely on a jack.
* Wear safety glasses: Flying debris is a possibility.
* Use gloves: Protect your hands from grease and sharp edges.
* Disconnect the battery's negative terminal: This prevents accidental short circuits.
Tools You'll Need:
* Jack and jack stands
* Wheel chocks
* Socket wrench set (metric and possibly SAE)
* U-joint press or hammer and punch (less precise)
* Torque wrench
* Driveshaft support (recommended)
* Penetrating oil (PB Blaster, etc.)
* Grease
* New U-joints (get the correct replacement for your driveshaft)
* Hammer
* Punch set
* Center punch
* C-clamp (possibly)
* Socket extension
* Ratchet
Procedure:
1. Preparation: Securely lift and support the truck. Remove the driveshaft. This usually involves disconnecting the driveshaft from the differential and the transmission (or transfer case if 4WD). You might need to remove the rear driveshaft yoke retainer bolt and nut. Note how the driveshaft is oriented.
2. U-Joint Removal:
* Using a press: This is the best method. A press makes it much easier and safer to remove the old U-joints without damaging the driveshaft. Clamp the driveshaft securely in the press and carefully press out the old U-joints.
* Using a hammer and punch: This method is more difficult and carries a higher risk of damaging the driveshaft. Use penetrating oil to loosen the caps. Carefully punch out the retaining clips (caps) surrounding the U-joint's bearing cups. Then use a punch to drive out the bearing cups. Be patient and persistent; it takes time and finesse.
3. U-Joint Installation:
* Using a press: This is far superior. Use the press to carefully install the new U-joints into the driveshaft yokes.
* Using a hammer and punch: With the new U-joint assembled (usually with clips installed), carefully tap the cups into place. Ensure that the clips are properly seated.
4. Grease the U-Joints: Pack the new U-joints with grease before installing them. This ensures proper lubrication.
5. Reinstallation: Carefully reinstall the driveshaft, ensuring it's properly aligned. Reattach the driveshaft to the differential and transmission (or transfer case). Torque the bolts to the manufacturer's specifications. Refer to your repair manual for the correct torque values.
6. Double Check: Inspect your work for proper alignment and secure connections. Lower the vehicle and check for any leaks.
7. Test Drive: Take the truck for a short test drive to ensure everything is working correctly. Listen for any unusual noises.
Important Considerations:
* Driveshaft Balance: After replacing U-joints, it's highly recommended to have the driveshaft professionally balanced. An unbalanced driveshaft can cause vibrations at higher speeds.
* Phase Alignment: If you are working on a 4x4, make sure to note the phase alignment markings of the driveshaft and transfer case. Improper reassembly can damage components.
* Repair Manual: Using a repair manual specific to your 1978 Ford F-150 is crucial. This will provide detailed diagrams and torque specifications, significantly increasing your chances of success.
Replacing U-joints is a hands-on job. If you're not comfortable with this type of repair, it's best to take your truck to a qualified mechanic. Improperly installed U-joints can lead to serious damage, potentially resulting in accidents.
