Needle bearings make use of small cylindrical rollers to carry out their function. The term “needle” implies that the length is much greater than the diameter; typically the L/D ratio is between 3 and 10. The main purpose of needle bearings is to reduce the amount of friction present at a rotating surface. Let's take a look at some of the ways in the automotive industry uses needle bearings:

These form an important part of many vehicle's combustion engines. They are responsible for the translation motion of the camshaft and for the opening and closing of the system's inlet and outlet valves. Along with other types of bearings, rocker arms often make use of needle rollers, in which two bearings mate with the axis of the rocker arm.   

Transmission

The automatic transmission system of a vehicle uses needle bearings as well as several other types of bearings. These bearings are usually collected within a round cylinder held together by assembly grease. Since the bearings are not fastened to the cylinder, they can fall easily from the carrier if not handled with care. The main purpose of the needle bearings contained within the transmission system is to reduce friction and control shaft endplay.  

Pumps

Needle bearings are also used in car pumps, where they provide radial thrust and offer combined loads with the help of careful alignment between the pump's shaft and the housing which carries the bearing mounted on it. Thus, needle bearings play the dual role of providing thrust while also keeping the shaft aligned in the correct position.

Compressors

The compressors that are housed within vehicles undergoes a great deal of pressure during the course of their operation. A great deal of friction is also generated, which can quickly wear out the internal parts of the compressor and result in poor performance. Needle bearings are added to compressors to ease the friction they are subjected to by distributing the load more equitably across their surface.

Drive Shaft

In a rear-wheel drive, the drive shaft usually carries as many as eight needle bearings, with four bearings present in each of the U-joints. More bearings can be added to the drive shaft if it is particularly long or if it needs to operate on steep slopes.

Benefits of Needle Bearings in Vehicles

Now let's take a look at some of the reasons why needle bearings are the preferred choice of bearings in automobiles:

1. Needle bearings have greater load carrying capability with respect to ball bearings, since surface contact is across a line for needle bearings, as compared to a point for ball bearings.  
   
   
2. With the help of needle bearings, friction is decreased significantly and torque is transmitted with great efficiency while dealing with static loads and oscillating surfaces.
   
   
3. Valve stem wear is also reduced with the help of needle bearings, since the load on the bearings is spread over a larger surface for increased durability.
   
   
4. There is also less added clearance in needle bearings, which means the difference between the diameter of the shaft and the diameter of the bearing is greatly reduced, making needle bearings far more compact than ball bearings.

Thus we see that needle bearings play a very important role in the automobile industry, and are responsible for keeping the internal components of the vehicles running smoothly with the least amount of friction.