What universal joints do and why they fail

A universal joint (or U-joint) connects two shafts that are not perfectly aligned — typically the driveshaft to the transmission and rear axle on rear-wheel-drive vehicles. It lets the driveshaft move up and down as the suspension bounces while still transferring power. The joint itself is a cross-shaped piece of metal with needle bearings at each end, held in place by a retaining clip or strap.

U-joints wear out because the needle bearings inside gradually lose their grease and begin to bind. When a U-joint fails, you will hear a clunking sound when you accelerate or shift into gear, feel vibration under the car, or notice the driveshaft has play when you grab it by hand. A failed U-joint can damage the driveshaft or transmission if you keep driving, so replacement is not optional once it starts to fail.

Replacement takes two to four hours depending on whether your vehicle has one U-joint or two, and whether the driveshaft is a one-piece or two-piece design. Most DIY mechanics can do this job with basic hand tools and a U-joint puller, though some vehicles require a press.

Key Takeaways

  • A U-joint connects the driveshaft to the transmission and rear axle, and fails when the needle bearings inside lose grease and bind up.
  • You will need a U-joint puller or a press, a socket set, a hammer, and a way to support the vehicle safely — a floor jack and jack stands are essential.
  • The driveshaft must be marked before removal so you can reinstall it in the same position, which prevents vibration and keeps the balance correct.
  • Most vehicles have the U-joint held in place by four retaining clips or straps that you remove with a socket, then the joint slides out and a new one slides in.
  • After installation, torque the retaining bolts to the manufacturer's specification — usually 14 to 20 foot-pounds — and test-drive to confirm the clunking is gone.

Tools and parts you will need

Gather these items before you start: a floor jack and jack stands, a socket set (typically 8mm to 15mm), a hammer, a U-joint puller (a three-jaw puller works, or a specialized U-joint tool), a replacement U-joint kit (which includes the cross, four bearing cups, and four retaining clips), and a torque wrench. Some vehicles use straps instead of clips, so check your owner's manual or a service manual for your specific model.

A U-joint puller is not expensive — most cost between $15 and $40 — and you can rent one from an auto parts store if you do not want to buy. A press is sometimes needed if the bearing cups are pressed into the yoke rather than held by clips; if your vehicle uses a press fit, you may need to take the driveshaft to a shop rather than do it yourself.

Before you buy the replacement joint, confirm the size and style. U-joints come in different sizes (1310, 1350, and 1480 are common), and using the wrong size will cause vibration or failure. Look up your vehicle's driveshaft size in the owner's manual or call a parts store with your vehicle's year, make, and model.

Removing the driveshaft and old U-joint

Raise the vehicle on a floor jack and find it with jack stands under the frame — never work under a vehicle supported only by a jack. Mark the driveshaft and the rear axle pinion flange with a paint pen or marker so you can reinstall the driveshaft in the same position. This mark prevents vibration that occurs when the driveshaft is out of balance.

Unbolt the U-bolts or straps that hold the driveshaft to the rear axle pinion flange — usually four bolts. Slide the driveshaft forward toward the transmission, which will separate it from the pinion flange. The front of the driveshaft may still be connected to the transmission output shaft; if so, you may need to support the driveshaft with a jack or have a helper hold it while you work.

Once the driveshaft is out, place it on a workbench. Use the U-joint puller to remove the bearing cups from the yoke. The puller works by tightening a center bolt that pushes the cross out of the yoke, which forces the bearing cups out. If the cups are stuck, tap the puller gently with a hammer to help it move. Remove all four bearing cups and the cross itself, then clean the yoke with a wire brush to remove any rust or debris.

Installing the new U-joint

Slide the new cross into the yoke, making sure it sits straight. Insert the first bearing cup partway into the yoke opening, then use the U-joint puller in reverse — place it over the bearing cup and tighten the center bolt to press the cup into the yoke. The cup should slide in smoothly; if it binds, stop and check that the cross is seated correctly.

Repeat this process for all four bearing cups, working opposite corners (top and bottom, then left and right) to keep the cross centered. Once all four cups are in place, install the retaining clips or straps. The clips slide into a groove in the yoke and hold the bearing cups in place. If your vehicle uses straps, bolt them down with the four bolts and torque them to the manufacturer's specification — usually 14 to 20 foot-pounds.

Check that the U-joint moves freely by hand. It should rotate smoothly without binding or play. If it feels stiff or loose, remove the bearing cups and check that the cross is the correct size and that the cups are fully seated.

Reinstalling the driveshaft

Slide the driveshaft back toward the rear axle, aligning the marks you made before removal. This step is critical — if the driveshaft is installed out of phase, you will feel vibration at highway speeds. Bolt the driveshaft to the pinion flange using the same bolts you removed, and torque them to the manufacturer's specification.

If the front of the driveshaft connects to the transmission, make sure it is fully seated on the output shaft. Some vehicles have a slip yoke that slides over the transmission shaft; if yours does, push it forward until it stops, then pull it back slightly to may support it is not bottomed out.

Lower the vehicle and test-drive it on a quiet road at low speed. Listen for clunking when you accelerate and shift gears. If the clunking is gone, the U-joint replacement is complete. If you still hear noise, raise the vehicle again and check that all bolts are tight and that the driveshaft marks are aligned.

When to take the driveshaft to a shop

Some vehicles use a two-piece driveshaft with a center support bearing, or have U-joints that are pressed into the yoke rather than held by clips. If your driveshaft has a center bearing, you will need to remove and reinstall it, which requires a press and careful alignment. If the bearing cups are pressed in, you will also need a press to remove and install them.

A shop with a press can do this work in one to two hours and will charge between $150 and $300 for labor, plus the cost of the U-joint kit. If you do not have access to a press or are not comfortable with the job, this is a reasonable option.

Frequently Asked Questions

How long do U-joints last?

U-joints typically last 100,000 to 150,000 miles, but this varies based on driving conditions and maintenance. Vehicles driven on rough roads or towing heavy loads wear them out faster. Regular lubrication through a grease fitting (if your vehicle has one) can extend their life.

Can I drive with a bad U-joint?

You can drive a short distance to a shop, but a failed U-joint can damage the driveshaft or transmission if you continue driving. The longer you wait, the more expensive the repair becomes. If you hear clunking, have it checked right away.

What is the difference between a U-joint and a CV joint?

A U-joint is used on rear-wheel-drive vehicles and connects the driveshaft to the axle. A CV joint is used on front-wheel-drive vehicles and allows the front wheels to turn while still receiving power. They serve the same purpose but are designed differently.

Do I need to replace both U-joints at the same time?

If only one U-joint has failed, you can replace just that one. However, if the driveshaft has two U-joints and one is worn, the other is likely close behind. Many mechanics recommend replacing both at the same time to avoid a second repair in a few months.

Will a new U-joint cause vibration?

If you marked and reinstalled the driveshaft in the same position, vibration should not occur. If you do feel vibration after replacement, check that the driveshaft marks are aligned and that all bolts are torqued to specification. Vibration can also mean the driveshaft itself is bent, which requires replacement.