You should determine the condition of your failing U-joint for you to estimate how long you can drive your bad U-joint. A car with a bad U-joint will break down in a few hundred miles at the maximum. But if you have a bad U-joint and you are having a transmission fluid leakage, you should not drive your car since the U-joint may break down anytime and will cause damage to the brake line, drive shaft, transmission line and other parts.
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When the U-joints fail completely, you can no longer drive your vehicle. You have no choice but have it towed to a mechanic. This is why it is important to know and identify the symptoms early on to avoid a complete breakdown of your car’s U-joint.
Typically, the U-joints last the lifespan of a vehicle. But as with any other parts in your car, it can break time any time and may need replacement. When you start noticing that they are not running as it should be, you should have them replaced as soon as possible. Another thing you should keep in mind is to replace them in pairs to save yourself from more troubles in the future. If it’s necessary for you to drive for a while with bad U-joints, do not run on 4WD as doing so can rip apart the shafts or make them explode. The safest thing to do is to seek professional help once you notice any sign of failing U-joints.
What’s the function of the U-joint?
The U-joint is the short term for Universal joint which refers to a rigid joint or coupling that has axis or rods that are inclined toward each other at a right angle or a 90-degree angle. U-joints are one of the main parts of the transmission system.
The function of the U-joint is to transfer rotational power from the engine onto the wheels of your car. One end of the U-joint is connected to the output shaft of the engine, and the other end is connected to the wheel’s axle.
Another purpose of U-joints is to adjust the height misalignment between the rear axle and the power transmission. They change the rotational power’s direction and transfer it to the wheels. They are not a typical, velocity-type joint. They are made to give torque and prevent speed fluctuations from happening. One of their awesome features is that they are dependable and noise-free in operation.
What happens if a U-joint breaks while driving?
If the U-joint breaks while you are driving, you will lose control over your car and it may tip over. This can lead to not only irreversible damage but also fatal accidents. As mentioned previously, a broken U-joint can damage the power transmission, brake line and other components of the car and can cause damage to the car or the driver.
How do you tell if a U-joint is going bad?
You can tell a U-joint is going bad or failing when you start noticing any of these common symptoms of a failing U-joint:
- Squeaking noise when you start to move your car forward or reverse – The bearing parts of each U-joint are greased at the factory, but may be without grease fitting to let further lubrication after the car is put into use which limits their service life. Because the bearing part of each U-joint twists a tiny amount with each rotation of the driveshaft (but always in the same place) the grease can be thrown out of the bearing cup or simply evaporate. With not enough grease, the bearing gets dry, resulting in metal-to-metal contact, and as the drive shaft rotates, the U-joint bearings will squeak. You will not hear the squeaking noise when the car runs faster than five to 10 mph due to other vehicle noise. The squeak is one of the signs that tell you that you should have your U-joint serviced by a mechanic. Doing so can extend the life of your existing U-joints.
- Clunking with a ringing sound when you shift from Drive to Reverse – Oftentimes, this noise is a sign that the U-joint bearings have enough excess clearance to let the driveshaft rotate slightly, then come to a hard stop, when power is reversed. This is the next phase of deterioration after having inadequate grease in the u-joint bearings. Unfortunately, when this happens, the damage can no longer be reversed but servicing or greasing the U-joint bearings may extend its life.
- Vibrations felt throughout the car while running forward at speed – Your U-joint bearings are worn enough to let the driveshaft move outside its normal rotational path resulting in imbalance and causing vibrations. This is a higher frequency type of vibration compared to that of an out of balance wheel because the driveshaft rotates 3 to 4 times faster than the wheels. The worn U-joint now wreaks havoc to other parts of the car including the transmission. At this point, you should have the U-joint replaced immediately to prevent more and bigger damage.
- Leaking transmission fluid from the transmission’s rear – A badly worn U-joint is usually the cause of having transmission fluid leaks from the rear of the transmission. The vibration mentioned previously has now damaged the transmission output shaft seal and worn the transmission tailshaft bushing causing transmission fluid to leak. When you suspect there’s a fluid leaking from the transmission, the transmission should be checked to identify the source of the leak, and to do the appropriate repair.
- Car can no longer move under its own power and the driveshaft is dislocated – When the driveshaft is no longer attached to the rear axle or transmission, it means your U-joint is completely kaput. The drive shaft is dislocated and can no longer transfer power. At this point, you will not only need to repair or replace the U-joint but you may need the entire driveshaft to be replaced or even more.
Are U joints hard to replace?
The replacement of the entire driveshaft is very easy, if not the easiest. Unfortunately, it is the most expensive fix. When there are compatible U-joints available, it will be worth the effort to replace all of them. You are lucky if you only have to replace your U-joints and not the whole driveshaft. In fact, you can even replace U-joints on your own. Replacing U-joints is not that easy but it is not hard enough for Here’s how:
Have the materials ready
First, you need to secure a U-joint replacement part. You will also need the following:
- Hammer or a U-joint tool or a Powerbuilt ball joint tool – to knock the car part out of its socket
- Jack
- A pair of jack stands
- Wrenches
- Socket
- Ratchet
- Some kind of ear protection (if you use the hammer method)
- A pair of snap ring pliers
- Grease gun
Prepare Your Car
U-joints are often seen in rear-wheel drive, front-engined vehicles, so you will need to have the rear section of your car lifted up. This can help prevent transmission fluid from leaking out. To lift the car as a whole and with its rear end a bit higher than the front end would be ideal. It should be raised high enough so you can place 2 jack stands on opposite sides of the vehicle.
Remove the half-shafts and/or driveshafts
Prior to unbolting, make sure to mark with paint the alignment and orientation of the shaft relative to the differential flange and the transmission. The driveshaft is balanced to rotate properly from the assembly line. It’s a must to restore it exactly the way it was assembled.
Disconnect the Universal Joint
One of the hardest parts in replacing a U-joint is removing the U-joint itself. This typically requires hammering the yoke in one direction, while holding the U-joint to resist the movement. This will help release the tension on the C-clip of the joint or the snap ring tension. Grab onto the U-joint’s caps to secure the yoke assembly and the U-joint. This will help in stabilizing the assembly while you are striking one side of the yoke with a hammer. You can remove the clip or the ring once you release the tension.
When using a U joint or ball joint tool, you must use the correct size of press cap. It must fit the yoke of the driveshaft. Put the press cap over the threaded rod of the U-joint tool. Obtain another press cap that is smaller than the opening of the yoke but is larger than the U-joint bearing caps. To help release the tension from the yoke, tighten the U-joint too threaded rod. Now you can remove the snap rings or clips. Keep on tightening the tool till you can push one bearing cap out of the yoke’s hole. Repeat the process until you remove the rest of the caps.
Install the New U-Joint
Have your new driveshaft U-joint replacement part with you. With a small amount of grease, lubricate the replacement cap’s inner surface. Place two opposing bearing caps on the replacement U-joint and secure them using a tape or a rubber band. Now insert the replacement U-joint’s polished ends into the holes of the yoke.
Put one of the bearing caps right under one of the openings of the yoke. Do a gentle tap on the yoke so it advances into the cap and help seat the yoke in the cap. You can now begin hammering the yoke once you are sure that the bearing cap is seated straight.
To secure the U-joint to the yoke, replace the C-clip or the snap ring. When you have a ball joint or a U-joint tool, insert the U-joint into the yoke’s opening and slide the one side of the yoke as far as you can. Push a new bearing cap as far as possible into the yoke. Push the bearing cap straight into the yoke with your ball joint. The cap should be properly seated before you attach the C-clips or the snap rings.
Put Everything Back
Now you can put back the driveshaft to its original position. Raise the driveshaft and align it with the yoke. Make sure that you observe the proper alignment of the yoke with the transmission and the driveshaft. This is where your markings come in handy. Attach the mounting clips again to help secure the driveshaft into the transmission. Place a jack under your car and lift the rear end of your vehicle. Take off the pair of jack stands and lower your vehicle to the ground. You can now remove the jack and secure your work area.
Go On A Test Drive
Take your vehicle for a drive to verify that the problems you’ve experienced prior to replacing your U-joint are no longer there.
Replacing your U-joints is not that hard. It only takes correct tools and a bit of elbow grease to get it done. But if the task overwhelms you, then better have a professional mechanic do the job for you. Want to know how much it costs to replace a U-joint? Click here.
Conclusion
Having a bad u-joint is a serious problem that should never be ignored. Once you start to notice any sign of a failing u-joint, you should have the problem addressed right away. Knowing the state of your u-joint will allow you to estimate if your car is still drivable to get to an auto repair shop. The better question to ask is if you can still drive your car with a bad u-joint, instead of asking how long can you drive with a bad u-joint.
You must check for transmission leakage. You can stop a minor lubricant leakage and drive to the nearest repair shop that has ready made seals to stop the leakage temporarily. Lubricants may extend the lifespan of a U-joint but ultimately you will have to replace your U-joint.
When there’s a complete breakdown of the U-joint, your only option is to have your car towed to a service station or contact a mechanic.