The first step is to look at the conditions under which your car or truck is vibrating. Does it only happen at certain speeds? In certain gears? Is it a noise, or a tangible sensation, or both? Where does it seem to be coming from? Can you feel it in the seat? How about the steering wheel?

90% of vibrations can be used by rebalancing the wheels. If balancing your tires doesn’t cure the shakes, check the tires and wheels. A bent rim, and out-of-round rim or tire, or an off-center wheel can all cause nasty quaking in your vehicle. Similarly, worn shocks or a bad suspension can make normal ‘road noise’ into a very violent vibration.

Failing all of those, the problem is likely to be the driveshaft. This problem happens only rarely in a front-wheel drive vehicle, because the driveshaft spins at the same speed that the tires do. That means that at 60 miles per hour, your driveshaft is turning at barely over eight hundred revolutions per minute — the shaft would have to be greatly out of whack for that low of an RPM to produce meaningful vibrations.

On rear-wheel and all-wheel- drive driveshafts, however, because the difference in front and rear suspensions require the driveshaft to be able to operate at a slight angle, the shafts utilize a series of joints that have the final result of causing the driveshaft to spin at a much higher rate. Driveshafts on these vehicles can cause horrendous shaking at high speeds with even a relatively minor ding.

A worn or merely incorrectly installed u-joint

can cause vibrations at any speed. Such joint will often clunk when the car is put into gear or changes gears abruptly. Somtimes, a regular chirping sound will happen when just getting the car into gear. All of these symptoms mean you should take your vehicle to a driveshaft mechanic immediately, or you risk serious damage.

The essence of a CV joint is movement — a properly-maintained joint can perform a myriad of contortions and movements, all without losing the ability to transfer rotational force from one end of the driveshaft to the other. Without the boot, such a joint would be jammed up in moments — and over time, as years of flexing and bending and a continuous abuse of salt, pebbles, and temperature changes take their toll, the boot can become brittle or wear thin and break.

As soon as that happens, the lubricant starts to escape, and water and grime get in. Eventually, the joint is completely ungreased, even if enough of the boot remains to keep larger contaminants out. Running dry, it wears out, and it’s just a contest of which will happen first — will a rock get into the joint and lock it up solid, or will the metal wear through and snap?

The first scenario leads to a car that simply stops rolling — if it happens at highway speeds, it will ruin your tires and wheels, or possibly even catapult your car end-over-end on the freeway! In the second scenario, the car simply loses power to it’s tires — but the driveshaft, snapped loose, can plunge inches into the surface of the road or can fly upward and pierce the machinery and floorboards above it, even jutting violently several inches into the passenger space.

So what can you do about a boot that’s worn through? Simple — get it replaced. If you catch it in time, that’s all you need to do. If not, well, you might have to replace the entire driveshaft. If you’ve got a custom car with a custom driveshaft, that can be quite a hassle unless you’ve got a great custom driveshaft shop like DynoTech.

If you’re concerned about your CV joint boots — and you should be if your car has been on the road for more than five or six years — here’s how to check them: look under your car. Jack it up, and look for the driveshafts — they’re the long rods that run from just below your engine to the four wheels. On each end of each driveshaft, there should be something that looks like a short black cone with accordion-like folds around it. Rotate the driveshaft and the tires to look at all sides of each boot, and make sure that they’re all intact.

If you find one that isn’t, take it straight to your local mechanic or custom driveshaft crew and get them repaired ASAP!

The best time to detect a driveshaft problem is any time you’re parked and you first put your car into gear to start moving. The transmission transfers power to the flywheel, which transfers it to the driveshaft, which is supposed to fluidly transfer the power to the wheels. If there’s a massive shudder, a sudden pop, or a grating crunch, you’ve almost certainly got a driveshaft problem.

There are several different kinds of driveshaft, depending on whether your vehicle is rear- or four-wheel drive, how heavy it is, whether it’s built for speed or towing power, and other factors. There are two elements you will always find on a driveshaft: a long tube (the shaft), and a u-joint (often a double-u, or CV — constant velocity –, joint). Almost all driveshaft problems are with the u-joint, though on occasion the tube can become dented or bent, which results in significant problems as well.

Diagnosing and Servicing the U-joint
The first thing to check on a U-joint is the ‘boot’, a rubber casing that surrounds the u-joint and protects it from dirt and rust. If the boot is cracked, clean the joint thoroughly and then test it for mobility. If the u-joint cannot move freely in all directions, it needs to be replaced. If it does move freely (or after swapping it out), add lubricant and put a new boot on it.

Diagnosing the Driveshaft
In most cases of a problem with the actual shaft, the dent or bend will be clearly visible, and the solution is a replacement driveshaft. If the vehicle in question has had significant suspension mods or any other modification that would change the height of one end of the car without changing the other equally, problems can arise from a tilted driveshaft.

Keeping the vehicle level, use a basic tool like a protractor to determine what angle the driveshaft sits at relative to the vehicle. If it’s more than eight degrees off of level, you run the risk of shuddering vibrations due to the u-joint’s inability to transfer power properly across that much of an angle.

Of course, there are many variations of driveshaft in modern cards, including split shafts, half-shafts, and different kind of joint — but the advice above covers the basics of what a skilled owner can hope to accomplish in their garage. If your problems are more complex, it’s best to contact a custom driveshaft company and have them take care of the work for you.

Of course, there are times when that convenience becomes terribly inconvenient — when your car breaks down, which, according to Murphy, must always happen at the least expected and most troubling time. Automotive experts have been telling us for years that we need to engage in preventative maintenance, but how do you know that it might be time for such maintenance when the part that’s in danger is a very solid item like the drive shaft?

What’s a drive shaft?
The drive shaft is the rod, usually between 2-3 feet long and usually either solid steel or solid aluminum, that forms one part of the connection between your engine and your wheels. Without a driveshaft, you could gun the engine all you want, but you wouldn’t get anywhere. Perhaps the most important thing you can know about your driveshaft is that it almost never breaks all at once — there are clear symptoms you can spot before the final event that will let an observant driver know that it’s time for a new driveshaft.

Symptoms
All vehicles vibrate as they drive down the road — that’s just a consequence of a running motor. But sometimes, your car vibrates significantly more, and it’s not because of the road. Even then, ninety percent of the time, the problem is with your wheels, not your driveshaft — so if you’re getting significant vibration, your first step should always be to get your wheels balanced.

Once you’ve done that, if the vibration doesn’t go away — especially while accelerating in a low gear — it’s time to talk to a drive shaft expert like DynoTech. In all likelihood, your driveshaft has acquired a flaw. If the problem is simple, like a cracked U-joint boot that needs cleaning out and replacement, you can probably get that done in a half-hour. Depending on your vehicle, however, a driveshaft might be just as quick, or take a few days if you’ve got a specialty vehicle that will require a custom driveshaft.

Measuring
The first step is to determine how long your driveshaft will need to be when your work is complete. Measure carefully, three or four times, and write the number down somewhere safe. If you lose that number, you’re lost.

Finding and Separating the Part
Take a basic metal grinder, and grind the weld between the tube and the fixed yoke down until it’s flush with the tube’s outer surface. Done correctly, you should just be able to make out the joint where the yoke and the tube meet. Then, grind in a further 1/16th to 1/8th of an inch until the part becomes clear (i.e. no signs of welding remain). Then tap the joint all the way around with a flat faced hammer until the two pieces separate.