A drive shaft is a cylindrical shaft that shuttles RPM and torque from your gearbox to the rear wheel differential (or a transfer case). The drive shaft rotates at the same RPM as the transmission’s output shaft.
Driveshafts are common in rear-wheel drive vehicles or four-wheel drive trucks with a transfer case. All front-wheel drive vehicles use a transaxle and two continuous velocity (CV) joints, while vehicles with any form of four-wheel drive, no matter how mild, will have some form of a drive shaft.
The driveshaft must be strong enough to withstand the torque while being light enough to avoid being dead weight to the car. Most manufacturers use steel alloys, aluminum, or carbon fiber to build their tubular transmission shafts.
Since the driveshaft will always be under high torque and rotating at a very high RPM, any imbalances or weakness will lead to failure or hard to ignore symptoms.
Top Signs That You Have a Faulty Drive Shaft
Since the driveshaft is integral to your car’s operation, you will get hard to miss cues once it’s faulty or in the process of failing. Even though you won’t get a check engine light, the symptoms tend to be very noticeable and different from anything you’ve ever experienced.
Harsh Vibrations From Under the Car Once You Get Moving
The first symptom most drivers notice from a faulty or failing drive shaft is harsh vibrations underneath the vehicle. The vibrations get intense as you pick up speed and don’t go away on their own.
If the problem isn’t addressed on time, the vibrations get worse and worse over time. Even though vibrations could also mean you have issues with your tires, a wheel is unbalanced, or you have a badly dented wheel, you should also have your transmission checked.
In most cases, the shaking is from worn-out bushings in your driveshaft. These bushings damp out tiny vibrations from a driveshaft that’s working perfectly. If they’re worn out, more of these vibrations will transfer into the car’s cabin.
Under rare circumstances, your driveshaft could be slightly bent or warped. This could happen if you offroad and hit an obstacle while crawling the rocks. While this is far-fetched, it could happen if your vehicle doesn’t have enough under armor.
Cracked or damaged bushings are easy to identify. Cracks are common in high mileage vehicles. Also, check your other suspension bushings as these could also wear out as they were installed at the same time as your driveshaft bushings.
If you can’t see a visible problem with the driveshaft, consider balancing your wheels and seeing if the vibration goes away. Wheel balancing is cheaper. It’s an excellent way to exclude unbalanced wheels as the cause of the vibrations.
A Clunking Noise When You Engage a Gear or Accelerate
Slipping in gear or accelerating ought to be very smooth in a well-working vehicle. Any clunking noises when you do any of the above hints at something loose or faulty somewhere in your drivetrain.
While this could be anything from the transmission itself to your transfer case, it could also mean that your driveshaft has a bad slip yoke.
A slip yoke assembly allows different shafts in a drive shaft to flex as they adjust to various torque inputs and requirements. Their flexing allows the U-joints joining the driveshaft components to take in more torque than they normally would if it were all transferred instantly.
Some little slipping reduces the impact force. If the slip yoke is damaged, it will either not slip enough leading to the jolt. It will yield too fast at other times, leading to a very fast and uncontrolled slip that ends in a jolt once its slip distance is over.
Other than a lose U joint, the shuddering could also be from a worn-out center bearing.
Squeaking Noises
Your car shouldn’t squeak and groan – especially when driving on smooth paved surfaces.
If you hear squeaks from under the car when on a very smooth road, it’s most probably from your driveshaft.
The squeak could be from the U joint, a balancer, or any other worn-out component in the drive shaft assembly. It could also be from a grease point that has dried up due to neglect.
ProTip: Squeaks and groans when driving over uneven surfaces could be from suspension components as the ups and downs make it travel more, amplifying sounds you won’t otherwise hear when on a smooth surface
The Universal Joint Doesn’t Move Isolating One Part of the Shaft.
Most driveshafts come in two parts. A U joint joins the section from the transmission to the section connected to the rear differential. You might have two driveshafts connected to a transfer case in the middle of the vehicle instead of a U joint.
Either way, your driveshaft could fail such that the rear portion connecting to the differential won’t spin even though the section from the transmission spins.
This means you have a faulty U-joint that isn’t creating a proper linkage between the two parts. While it’s rare for a U joint to fail this way, it could happen sometimes. When it happens, the cap seals or bearings in the U joint.
A part of the shaft not spinning is more common in vehicles with a transfer case. Transfer cases are more complex and could fail to isolate a part of the drive shaft.
Your Car Shudders and Seems to Lose Power Intermittently
Shuddering and intermittent power loss will accompany one or more of the problems addressed above so far.
The shudders happen when a loose U joint, stuck or failing bearings, and sometimes damaged spline gears slip as you push power through them. You will feel the impact more under high torque applications, such as going up a hill, towing, or rock crawling.
Don’t ignore the shuddering. It could cause more damage to your gearbox, transfer case, or transmission; Have a mechanic look into it as soon as possible.
Your Car Has Problem Turning
A damaged drive shaft not only has trouble transmitting power to the rear wheels. It could also limit how they behave when turning.
It could be stiff enough to prevent them from turning correctly. This increases your vehicle’s cornering radius while also making it harder to maneuver the vehicle.
Your car will be dangerous, and you could quickly lose control.
Can You Drive With a Broken Drive Shaft?
Driving with a broken driveshaft isn’t wise. The possibility of even moving the car depends on how broken the drive shaft is.
Slight damage that keeps it moving with some slippage could let you crawl your car home.
However, if the break totally damages the shaft and even dislocates it at one point, your car will be undrivable. The driveshaft can’t transmit power to your rear wheels, and you have no way of putting down power from your gearbox through the tires.
Moreover, trying to drive with a broken shaft poses a more immediate danger. A loose chunk of metal spinning at the excess of 1k RPM is a dangerous missile should it come loose.
It could tear a couple of things apart and potentially harm the driver or anyone near the vehicle.
Some four-wheel-drive vehicles might keep moving using power from the unaffected drive tires. However, this will cause premature wear to the transfer case or center differential – especially if the damaged driveshaft sent power to the main drive wheels.
What Causes Drive Shaft Failure?
A couple of things could cause driveshaft failures. Knowing them will help you identify risk scenarios and inspect your driveshaft more often if you subject your vehicle to such scenarios.
You Tow or Carry Heavy Stuff
Towing or carrying heavy things puts different parts of your driveshaft under strain. Most trucks are designed to take this in. However, the more you push it, the more likely you are to replace parts of the drive train.
Your U joint, bearings and the slip could give up over time. The failure could be gradual and eventually lead to instant failure if you keep pushing your vehicle.
Take good care of your vehicle if it’s a workhorse. Inspect your entire drive train and engine more often to identify potential failures and fix them before time. You can avoid such scenarios by ensuring that you only work your car to acceptable spec.
If you need more power, look for a bigger, more powerful vehicle with a bigger payload and more towing capacity.
You Offroad a Lot
There’s nothing as exhilarating as a powerful truck conquering seemingly impossible offroad trails. Crawling over rocks and driving through mud puddles with seeming ease.
While impressive, offroading puts your vehicle’s delicate underbelly at risk. This is why many offroaders have dedicated undercarriage armor to deflect impact and protect crucial components.
However, taking your vehicle out into the open puts it at risk regardless of whether you have under armor or not.
Should something sharp strike or push against your drive train, chances are it will either break loose or put undue pressure on some joints. At times, the impact could even slightly bend the shaft.
The result is squeaks and vibrations that force you to replace or repair the shaft to keep your vehicle working optimally.
You Drive an Old Car
Cars get problematic as they age. More and more components start failing. The most common are moving parts that are under high stress.
This is a perfect description of the drive shaft. Over time, its bushings, the U joint, the slip, splines at the end, and other moving parts in the shaft assembly start to wear out.
As they start working out of specification, you will start noticing the lousy driveshaft problems we highlighted above. Ignoring the symptoms will lead to further failure, leaving you with more damage and the need to fix or replace the entire system.
What Happens When a Drive Shaft Breaks While Driving?
Sometimes, the drive shaft can break when you are on the road. If this happens, you will feel an instant loss of power to the wheels.
As the engine unloads as it no longer feels a load from the wheels, the RPM on the engine will instantly jump. If it is automatic, it could even gear up thinking that the car is cruising.
All along, your vehicle will be slowing down as the power won’t be getting to the ground.
As for the broken shaft, chances are it will rest on a protective chain (assuming your vehicle has one) or remain trapped between the car and the ground.
If it has enough momentum, it could beat around for a while leading to loud clunks and bangs. Sometimes, you could get some cosmetic or structural damage under your vehicle.
Whatever you do, slow down and stop as soon as you hear the noises and detect the loss in drive power. Luckily, it is impossible to ignore the commotion a broken drive shaft causes.
Can a Bad Drive Shaft Damage the Transmission
While your transmission is designed to handle all the strain the engine can put it through when driving a properly loaded vehicle, it expects the power demands to be smooth.
A transmission expects to start driving the vehicle smoothly and keeping pushing through torque gradually.
A driveshaft that clunks and jerks are the exact opposite to this. It deals occasional hammer blows and impacts to the transmission every time it clunks.
This impact could be enough to shear gears on the output shaft, stress the torque converter, or burn the clutch faster.
Get your faulty drive shaft fixed or replaced before it takes other components in the drive train.
If it doesn’t affect the transmission, it will affect the transfer case or your rear differential.
How to Fix a Damaged Drive Shaft
Fixing a drive shaft depends on what is damaged and has to be replaced. Replacing the entire shaft could cost between $500 and $2000 depending on your vehicle and the type of driveshaft you go for.
If you opt to repair parts of the shaft, for instance, the U joint, you will spend way less. Sometimes, repairing a creak might be as easy as greasing and lubing up a dried-up moving joint.
Why Does My Drive Shaft Keep On Breaking?
A couple of things could keep your driveshaft breaking. In most cases, the drive shaft breakage is at the U joint. In rare cases, another portion of the shaft could shear and snap.
Here are the top reasons why your driveshaft keeps on breaking.
It is too Small for the Setup
A drives shaft that’s too small or too weak will keep on snapping. Driveshafts come from the factory designed to match your vehicle’s payload and wheel size. Overloading will damage your shaft faster.
Another common damage is a motor upgrade to way bigger tires for better offroading and overlooking changing your driveshaft. That’s simply too much torque requirements than your stock shaft was designed to handle
Too Much Flexing and Binding
A lift kit in a truck changes the angle a driveshaft has to take to link up with the rear differential.
Lifting your vehicle a lot will force the differential to flex too much as the suspension travels. The angle gets too shallow with the differential under full load and at a steep angle with the suspension offloaded.
This flex will eventually fatigue the drive shaft’s metal, causing it to snap. Before this happens, chances are your U-joint, and other bearings in the system will break before the actual shaft metal snaps.
Check this too: Why Is My Engine Idling Rough?
Bottom Line
You don’t have to worry about your driveshaft failing you unless you put it under too much strain. If you modify your vehicle to handle bigger wheels and more power, be sure to swap your driveshaft too. The same applies if you install a lift kit or drive an old vehicle.
Otherwise, driveshaft failure would be unheard of in a regular road-going vehicle that’s still under warranty. In this case, you don’t have to worry. After all, it will still be under warranty, and the manufacturer will fix it if you didn’t tamper with the car or damage it when offroading.