The Drive Train

The drive train is made up of a variety of components and varies based on details about the vehicle. Some of these components include axles, constant velocity (CV) joints, a driveshaft, U joints, a transfer case, and differentials.

U Joints

U joints are used in most rear wheel drive vehicles. Since the engine is mounted at the front of the frame, the rear wheels must be able to move up and down in response to the road conditions. Universal joints, or U joints, allow this to happen.  

Two U joint would be used, one to connect the drive shaft to the transmission at the front of the vehicle and one to connect the drive shaft to the differential and rear axle assembly at the back of the vehicle. We carry 3 lines of U joints: NAPA Proformer, Precision Premium series, and Precision Super Strength series. The NAPA line of U joints is a high quality bearing design that meets OE specifications and is the most cost effective. The Precision Premium series is designed to withstand extreme loads and high torque. Finally, the Precision Super Strength series is enhanced to withstand heavy duty, agricultural, and off road use. Call or come in to your local store if you need advice or recommendations about what part will be right for you. 

CV Joints

Constant velocity, or CV joints are used instead of U joints in front wheel drive vehicles. In vehicles with CV joints (or, an assembly refereed to as a CV axle), the transmission and differential will be housed in a single unit, called a transaxle. Power from the transaxle moves through the axle shafts to the wheels. CV joints fitted onto each end allow these axles, or half shafts, to move the vehicles suspension.

We carry both new and re-manufactured shafts. The NAPA Max Drive Re-Manufactured line replacement shafts are sold on an exchange basis. 

 They come with re-manufactured outer CV joints that have been precision ground. Each joint is reassembled with 100% new internal components.The NAPA Max Drive New line of CV axles are 100% new components which meet or exceed OE specifications.


The differential is a part that allows one wheel to move faster than the wheel directly across from it. This is important to allow the outside wheel to move faster during a turn. The placement of the differential depends on whether the vehicle has front or rear wheel drive, or both!