If you do a lot of your own automotive work, you may already know how the U-bolts work under your solid axle vehicle, but replacing the U-bolts is a big job, and you must use the right parts for your vehicle.

Understanding U-bolts

There are several places that U-bolts are used on a vehicle, but the most common is to secure the axle housing and the leaf springs together on trucks and older cars. The U-bolt wraps around the axle housing, and the top of the bolt goes through a plate on either side of the axle. Large nuts are used to secure the assembly together. 

The other common place you will find U-bolt is on the ends of the driveshaft. The U-bolts loop over the U-joints in the driveshaft and secure it to the transmission and the axle housing on the opposite end. While these are both automotive U-bolts, they are different in the way they are used, and the sizes and properties vary greatly. 

Suspension U-bolts

Every car or truck that uses U-bolts to secure the axle to the springs works the same way, although in some cases, the spring is above the axle and sometimes positioned under it. In either case, the U-bolt needs to be the right size to fit the vehicle. 

The size of the U-bolt includes the wire size (this is the diameter of the material the bolt is made from), the length of the U-bolts, and the size of the curve or U section of the bolt. If any of these things are wrong, the U-bolts will not fit on the axle properly. The amount of stress on the U-bolts could cause it to fail if you are not using U-bolts of the right size or dimensions. 

Visit the parts counter at your local dealer or go to a large auto parts store and have them check the size of the U-bolts required for your year, make, and model before you purchase U-bolts. Even if the size is right, the material the bolt is made from may be different from one car to the next. 

Driveshaft U-bolts

The U-bolts used on a driveshaft are much smaller, but the same rules apply when replacing them. You need to make sure you are getting the right part of they will not fit properly. There is very little space to spare when installing driveshaft U-bolts, so a bolt that is too long could impact the driveshaft as it turns, causing damage to the bolt and the driveshaft.

If you are not sure you have the right bolts for your vehicle, double-check the part numbers before using the U-bolts. Contact a company like Gitt's Spring Company to learn more.