How to Change U Joints on Vehicles
Universal joints (U joints) are located at both ends of a vehicle's driveshaft. As the driveshaft transfers power from the transmission to the differential, U joints allow the rigid shaft to "flex" without breaking. A U joint consists of two U-shaped yokes that hinge on a common cross-shaped piece. The four round ends of the cross rotate on needle bearings contained within caps that are fitted tightly inside the yoke flange bores. Worn or damaged U joints are dangerous, and should be replaced immediately.
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Things You'll Need
- Scribe
- Large flathead screwdriver
- Needle-nose pliers
- Locking pliers
- U-joint press
- Wrenches and sockets
Instructions
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1
Support the vehicle on jack stands. Index the yokes by scribing matching alignment marks on both yokes of the front and rear U joints. This will allow you to align the yokes in the same position when you reassemble each U joint. Also scribe a mark on the transmission end of the driveshaft so you can orient it correctly upon reassembly.
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2
Remove either the U bolts or straps and bolts securing the rear U joint cross to the pinion gear flange. Using a large flathead screwdriver, pry the driveshaft forward. Pull the shaft down, away from the pinion gear flange. Pull the driveshaft away from the transmission until the slip yoke clears the output shaft.
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3
Place the driveshaft on a table that is long enough to support the entire shaft. Using a screwdriver and needle-nose pliers, remove either the internal C clips or (depending on the model) the external snap rings securing the bearing caps.
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4
Attach the U joint press to the joint, and press out the first bearing cap. If the cross is not long enough to accommodate pressing the cap out completely, grasp the cap with locking pliers and pull it out.
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Reverse the press, and press out the other bearing cap. Gently angle out the cross, being careful not to score the bores in the yoke flanges.
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Carefully remove two opposing bearing caps from a new cross, taking care to ensure that the needle bearings don't fall out (high-temp wheel-bearing grease will hold them in place, if needed). Angle the cross into the flange bores. Slide the new bearing cups into the bores until the ends of the cross slip inside them (make sure that none of the needle bearings slip out of place while installing the cups).
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Press the cups just past the retaining ring grooves with the U joint press, and install either the new C clips or snap rings.
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Remove and replace the cross and bearing caps on the U joint connecting the driveshaft to the slip yoke using the same procedure.
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Taking care to orient the driveshaft properly (realigning your mark), slide the slip yoke back onto the output shaft. Aligning the scribed marks on the rear U joint, install either new U bolts or straps and bolts.
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Tips & Warnings
Buy the right tool for the job. There are many low-tech methods for repairing U joints, but they are better left to experienced mechanics. To prevent injury and damaged parts, use a suitable U joint press. Consult the manual covering the specific make and model of vehicle you are working on. Procedures vary, so always match part numbers, removing/installing them according to the manufacturer's specifications.
Never work under an improperly supported the vehicle. Always use jack stands that have been placed on solid, level ground. When working overhead, pay attention! Parts and tools can fall, causing injuries. Grease oil and other fluids can splatter, so always wear approved eye protection.
