The twisting force produced by the engine is called torque. The job of the drive shaft is to transmit this torque to the wheels of the vehicle.
Most vehicles are front-wheel drive, so the torque would be transmitted to the two front wheels with what’s called a half-shaft. But other vehicles have what’s called a drive shaft.
Would you be able to tell if there was something wrong with your drive shaft? Here’s how a drive shaft works and some common signs that would indicate a problem with this component.
What is a Drive Shaft?
A drive shaft (also called a propeller shaft) is essentially a long rod that is designed to transmit torque from the output shaft of the transmission to the rear differential in a rear wheel drive, four wheel drive, or all wheel drive vehicle.
A drive shaft will often have internal splines on the end that connects to the transmission and a universal joint (U-joint) on the end that connects to the differential.
In the case of a four wheel drive or all wheel drive vehicle, you may find that it actually has two separate drive shafts: one for transmitting power to the front and another to transmit power to the back.
This will depend on the manufacturer’s implementation of the four wheel drive or all wheel drive system.
Common Bad Drive Shaft Symptoms
Since drive shafts rotate quickly, they’re able to move the rear wheels of your vehicle. The only way they can keep rotating quickly is if they remain weighted down and balanced exactly right.
When the drive shaft begins to have malfunctioning issues, then your driving ability will be impaired. More specifically, there are 5 common symptoms you can recognize that will let you know there is a problem with the drive shaft or slip yoke.
If you’re driving the vehicle and you feel a lot of harsh vibrations coming from under it, then your drive shaft may be in trouble. This is usually the first symptom that people recognize when there is a drive shaft problem.
The vibrations are likely due to worn out bushings of the drive shaft. These bushings are what normally keep the drive shaft from vibrating in the first place.
If the problem is not fixed soon, the vibration will get more severe. It will get so bad that your passengers will be able to feel it too. The worst part is that other drivetrain components can also be affected and damaged.
Note that vibrations that increase with speed may mean your tires need to be balanced. This should be done regularly. Check your owner’s manual for the manufacturer’s recommendation.
2) Clunking Noise
When you accelerate your vehicle, do you hear a clunking noise? How about when you put the vehicle into reverse, or even into drive?
If you hear clunking noises in any of these cases, then it could mean your drive shaft has an issue and should be promptly inspected. Often, this is a common symptom of a bad slip yoke.
3) Squeaking Noise
If you’re driving and you hear a squeaking noise that is consistently coming from underneath your vehicle, then it is a sign that your drive shaft could be faulty. It could possibly be out of balance or some other part of it could be worn out.
4) Universal Joint Movement
If the U-joint of your drive shaft rotates too fast or fails to rotate, then it’s a problem with your drive shaft. The cap seals of the bearings could have rust on them. Either that or the u-joint itself is not stable.
You’ll need to have your drive shaft replaced because you can’t drive your vehicle in this condition.
5) Turning Problems
If you try to make a turn with your vehicle and the wheels don’t turn immediately or they hesitate, then you have an issue with your drive shaft. The tires will have a lot of resistance which you’ll be able to feel as you try to make a turn.
Obviously, this is a serious issue and it needs to be looked at right away.
If your steering wheel is simply difficult to turn, you may need to take a look at the power steering pump.
Can You Drive With a Bad Drive Shaft?
While it is usually possible to drive with a bad drive shaft, it’s usually not very wise to do it for long. If part of the drive shaft were to snap, you’ll lose power to that axle in the best case scenario. The drive shaft may fall and get wedged between the ground and your vehicle, restricting forward movement.
On some four wheel drive or all wheel drive vehicles, disconnecting one axle like this may stress the center differential or transfer case. This could cause premature wear or even failure of the center differential.
Before Subaru started mainly using CVT transmissions, they used a viscous coupling center differential. This type of differential is very sensitive to prolonged speed differences between the front and rear axles.
If the drive shaft were to disconnect on one side while it’s still spinning quickly, there is a good chance it will do massive damage to the underside of your vehicle. Remember that if one end is still connected to the vehicle, the drive shaft will continue spinning for a moment and take out anything in its path. This could be handbrake cables, brake lines, fuel lines, and even parts of the wiring harness.
Drive Shaft Replacement Cost
If you’re just replacing a half-shaft for your front wheel drive car, then it will cost anywhere from $470 to $940. You can expect the parts cost to be anywhere from $320 to $750, while the labor costs are only around $150 to $190.
If you have a rear wheel or four wheel drive vehicle which has a long drive shaft to power the rear wheels, then expect to pay somewhere in the range of $600 to $2,000. Keep that in mind that the type of vehicle plays a major role in both the price of parts and labor.