The drive shaft is the part of your car that takes the engine’s power and sends it to your wheels in order to propel the vehicle. There are two driveshafts in front-wheel drive cars, called half shafts. Rear-wheel drive vehicles have one driveshaft that runs the distance from the front to the rear of the car.
It’s very simple to tell when there’s a driveshaft problem – the car will not move, even if the engine is running. This typically occurs due to breakage, either from undue strain, age, or a combination of these factors. It’s fairly uncommon for the driveshaft to break but if it does, you’re going to need a new one. You’ll want it to be very durable because of the tremendous amount of stress it must endure.
Some things to look out for to make sure you’re getting a good quality driveshaft include:
Choose the correct balance of ability to bear power and price: A driveshaft that is too weak to support the engine’s horsepower will quickly meet its end, but one that is able to transfer more power than the engine provides will cost you more without delivering any additional benefit.
Go with OEM or OE-rated construction: These steel driveshafts are able to handle 350-400 HP, which is more than adequate for most street cars. If you’re interested in racing and performance capabilities, you could go with carbon fiber or aluminum, which are much pricier.
Purchasing a driveshaft custom-made to your application isn't difficult, but it is important to get it right because an improperly sized driveshaft can cause real problems. Too short and the slip yoke can come all the way out of the transmission and leave you stranded on the track. Too long and the end of the driveshaft can be smashed into the transmission causing expensive damage.
To measure for proper driveshaft length, begin by making sure the car is at ride height. You will need to be able to crawl around underneath it, so getting the car on wheelstands is a good idea. Just make sure it isn't raised with jackstands underneath the framerails so that the suspension is in full droop. Obviously, the rearend and transmission you'll be racing have to be in place and fully assembled.
Next, take the slip yoke that will be used on the final driveshaft (or one that's just like it) and insert it into the transmission's tailhousing until it bottoms out. Pull it back out 3/4 to 1 inch--this is your safety margin to make sure you aren't banging the slip yoke into the transmission's output seal once the racing gets started. Now, measure the distance between the centers of the U-joints on the transmission and rearend.
Quality CV joints: If your driveshaft comes with the CV joints attached, look for high quality materials like neoprene boots, as these resist cracking, which will decrease the chances of having to replace the entire driveshaft again due to CV joint failure.