The drive shaft in your car is what transmits torque from the engine to the wheels. If you have a rear wheel drive vehicle it's going to connect the rear transmission to the drive shaft. The output shaft from the transmission rotates and causes the drive shaft to spin and that in turn makes the wheels rotate thanks to something called the differential ring gear turning. It gets a little complicated, but the basic point here is that the drive shaft is what allows the motion created by the engine to turn into the motion in your wheels which propels your vehicle forward. If something goes wrong with your drive shaft, then your car is not going to be getting very far at all. And if you're noticing noise from your drive shaft when you're accelerating, that could indicate a problem that you're going to need to have addressed sooner rather than later.
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It's worth remembering that if you have a front-wheel drive vehicle, you don't have to worry about the drive shaft. A front-wheel drive vehicle gets its torque transmitted to the front wheels from the half shaft. The drive shaft is just what is used to transmit the torque in a rear wheel drive vehicle.
The drive shaft has to rotate at an incredibly high speed and the torque has to be extremely precise. Everything that gets thrown off in the way your drive shaft works is going to have a profound impact on your vehicle's performance overall. Also, it can cause some extensive damage to your drive shaft if it's not working the way it's supposed to. Let's take a look at some of the most common problems that can occur with your drive shaft and what could make it start producing noises when you're accelerating.
What Exactly is a Drive Shaft?
Also known as the propeller shaft, the drive shaft is basically just a long rod that connects the output shaft of your transmission to the rear differential in your rear wheel drive or four-wheel drive vehicle. Without the drive shaft your engine will not be able to transmit the motion that it creates as the pistons rise and fall of the cylinders to the wheels which would allow them to turn. It is the drive shaft that connects these two parts together allowing your entire vehicle to move.
What Does a Bad Drive Shaft Sound Like?
There are a number of components that need to work precisely in time with each other in order for your drive shaft to work properly. When they begin to fail, especially the bushings or bearings that support the driveshaft, as well as the U-joint in the drive shaft, you may end up hearing a handful of different sounds.
Generally speaking, a bad drive shaft is going to create a kind of rattling or clunking sound. You may also hear sounds that are like a high-pitched squeaking or a scraping noise of metal on metal. All of this will originate from underneath your car, rather than in the engine compartment. If you're hearing a squeaking even at low speed that picks up pace as you accelerate then that's probably your U-joints which requires some lubrication. If it's more of a knocking sound that is probably a problem with your CV joint.
U-joint Noises: If the problem is with the U-joints in your vehicle, also known as universal joints, it can be a result of them being worn down. This leads to rattling and scraping sounds when you are driving.
Bad Bearings: Inside your drive shaft are some rubber bearings that can wear out over time. When these go bad not only will you experience vibrations, but you're going to be hearing some noticeable grinding sounds when these fail on you.
Loose Drive Shaft: if your U-joints have failed then that is going to cause your drive shaft to come loose as well. The noise created by this may become more excessive when you're actually braking or turning rather than just accelerating. It's possible that if this is allowed to go on long enough the drive shaft completely falls out from your vehicle and the sound you hear will be the drive shaft literally scraping on the road under your car.
Typically, a drive shaft that is no longer balanced, or if part of it is wearing out, is going to make a noticeable and persistent squeaking sound.
Tube Failure: There's a tube in the centre of your drive shaft that spins along with it. However, if you overtax your drive shaft you can cause that tube to break which will create clunking noises while you're driving. This is usually the result of trying to tow more than your vehicle is able to pull.
Bad Slip Yoke: If you've never heard of a slip yoke before, it is a part of your drive shaft. It is what is known as a splined shaft that is connected to your drive shaft by the universal joint. It transfers power from the transfer case to the driveshaft and slides in and out of the transfer case. This in and out motion allows it to change length in response to your vehicle's movements along the road. If you have a bad slip yoke in your drive shaft, it can produce clunking noises in your vehicle.
Other Signs of a Bad Drive Shaft
Aside from the potential noise you may be hearing when you're accelerating there are a handful of other potential side effects of a bad drive shaft as well.
Vibrations: If you're noticing some intense and unusual vibrations coming from underneath your vehicle it's possible that the drive shaft is the source of the problem. If the U-joint that is part of the drive shaft begins to wear out, or the bushings that are in it fail, the driveshaft will begin to vibrate noticeably in a way that you can feel through the bottom of your vehicle. Your drive shaft is meant to be very well-balanced which completely eliminates any potential vibrations when it's operating properly. When you start noticing this vibration it means that your drive shaft has now gone out of balance and the situation will likely get worse until such time as you are able to get it repaired. If it's not repaired soon enough it could potentially damage the drivetrain of your vehicle so badly that it would render it undrivable.
Problems Turning: Because the drive shaft is responsible for converting the movement created by your engine to movement in the wheels of your vehicle, when your drive shaft isn't working the way it's supposed to it can prevent your wheels from doing what you want them to do when you turn the steering wheel. This is most prevalent when you try to turn left or right in your car. You will have limited control over how your wheels move and it can be very difficult to get your wheels to actually fully turn in one direction or the other. As you can imagine this is a very serious problem that you're going to need to have addressed as soon as you possibly can. If you are unable to turn your vehicle because the drive shaft is not responsive, you are at a high risk of having an accident.
Can I Drive with a Bad Drive Shaft?
It's definitely possible that you can keep driving with a bad drive shaft. If it has slipped out of balance, then it is these annoying sounds and vibrations that will first alert you to the problem, but your vehicle will not stop running as a result. However, just because it will continue to drive doesn't mean it's necessarily a good idea to ignore this problem.
If your drive shaft has come loose or slipped out of balance, then you're going to want to get it looked at as soon as you possibly can. The longer you allow this problem to continue the more likely you are to suffer greater problems with your drivetrain. You could potentially damage the U-joints, the axles and wheels themselves, not to mention your transmission as well. And, as we said earlier, a loose drive shaft could even possibly slip right out and hit the road under your vehicle. That could be not just an expensive repair bill, but a serious accident waiting to happen.
If your drive shaft were to break while you're driving, then the axle would stop turning and you would no longer have control over those Wheels. When it slips out, if it were to hit the road it could create a wedge that locks up your back tires and leaves you unable to control your vehicle. If that were to happen while you're driving down the highway with other cars it could be catastrophic.
You're also potentially causing damage to the transfer case or your differential as well if you continue to drive with a bad drive shaft. In the most serious circumstances if your drive shaft were to come loose while you are driving your vehicle it will continue to spin and potentially tear apart anything under your vehicle that comes in contact with it. You could end up causing damage to your brake lines and fuel line as well.
What Does it Cost to Replace a Drive Shaft?
Depending on the nature of the problem and whether or not you have a front-wheel drive or rear wheel drive vehicle will definitely have an effect on the price of this repair. If it is the half shaft you need to replace in a front-wheel drive vehicle it could potentially cost anywhere from $450 to $1,000 to get this replaced. However, if it is your drive shaft at the rear of your vehicle you may end up spending anywhere from $500 to $2,000 to get the driveshaft repaired. Obviously, this is quite a big range and the make, model, and year of your vehicle plays a heavy part in determining just how much it's going to cost to get the drive shaft of your vehicle repaired.
If you have a rear drive vehicle you can probably expect to pay around that $2,000 mark. However, for the average car on the road, you're looking at somewhere between $400 and $600 to get this problem fixed for you. Something like a Ford Focus or a Nissan Altima is going to cost you around $500 for this job to get done. On the other hand, if you're driving a Honda CR-V or a Honda Civic it might end up costing you well over $1,000. Obviously, this also depends on where you live and the mechanic you take it to since you can get a pretty large variance in prices even within the same city from one mechanic to another.
The Bottom Line
The driveshaft in your car is one of the least understood and least recognized parts of the entire vehicle. Most of us as drivers on the road have never thought about the drive shaft or what it does, and we certainly don't worry about any kind of maintenance or repair work to it because it's not typically something that falls apart. Responsible drivers know that they need to change their oil, get a fuel filter replacement, rotate their tires and that sort of thing. However, you expect that a drive shaft is going to last the lifetime of your vehicle and if something does go wrong with it we typically aren't even aware that it's the source of the problem because it's such an unusual thing.
Knowing the symptoms of a bad drive shaft are important to helping you diagnose exactly what's happening in your vehicle which in turn lets you know what you need to do about fixing it. The sounds your driveshaft makes when it's failing can help you better understand what's going on which means you can save time and some worries when it comes to wondering what went wrong in your car and what you're going to need to do to fix it. When you start noticing the sounds of a bad drive shaft, make sure you get into a mechanic as soon as you can to get the problem fixed before a bad situation becomes much, much worse.