U-Joint Sizes and Strength Comparison (2024)

U-Joint Angles and Binding

While u-joints are a simple way to transfer torque through an angle, they are far from perfect. Anything outside of a straight line will cause the yokes to bind, creating increased leverage forces on the u-joints and four speed changes during every rotation. These effects get more dramatic as the angle between the two shafts increases meaning that steering axles are at their weakest and most off-balance position when they are at full-turn.

Constant Velocity Joints
Constant velocity or "CV" joints eliminate binding and speed changes during rotation, however, they are more expensive and mainly used in independent suspension vehicles and some Toyota and Mercedes straight axles. Driveshafts with properly phased u-joints with matching input and output angles will also have constant input and output speeds because the misalignment angles cancel themselves out.

Front Axle U-Joints (Wheel Joints)

U-Joint Width vs. Cap Size
U-Joint sizes change based on two factors, the overall width of the cross and the diameter of the caps. Larger caps result in a stronger joint, while a larger cross will usually allow for more misalignment. For example, both 1310 and 1330 U-joints use 1.062" diameter caps, however, the 1330 is .406" wider and allows for more misalignment.

Axle U-Joint Strength Ratings
U-joint strength depends on the type of steel it is made from as well as the size of the body, bearings, and caps. They are rated by continuous torque loads which are calculated based on the full expected life of the u-joint. Catastrophic failure ratings are estimated to be 2 to 3 times listed yield torque.

Competition U-Joints
In extreme applications where axles are fitted with aftermarket 4340 Chromoly or 300M alloy axle shafts, standard u-joints would be an unwanted weak link. Companies like Yukon, OX, and CTM make extra strong, race-only style u-joints that can handle big tires and horsepower, however, these joints typically require daily lubrication and servicing that make them impractical for everyday use.

RCV Chromoly CV Axle Shafts
While competition u-joints do provide great strength, they still have the same u-joint faults listed above. To get the ultimate in strength and reliability, u-joints need to be replaced with heavy duty constant velocity (CV) shafts. RCV 4340 Chromoly and 300M CV axle shafts are twice as strong as standard u-joint axles while providing constant input and output speeds all the way up to 45 degrees. They are so strong, in fact, that RCV backs them with a limited lifetime warranty that even covers oversize tires and high horsepower in race applications.

Driveshaft U-Joints

Standard OEM Driveshaft U-Joints
Driveshaft U-joints come in hundreds of different variations, however, the following six sizes are by far the most common.

U-Joint Models and Part Numbers

Driveshaft U-Joint List
U-joint models and part numbers have mostly remained consistent over the years, however, many joints have been replaced due to slight improvements and thus there may be numerous designations for the same u-joint model. The table below contains a list of the most common automotive u-joints as well as their various other part numbers.

Axle U-Joint List
The table below contains a list of the most common wheel joints along with their previous and/or additional part numbers.

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Thick Gears and Carrier Breaks - A detailed explanation of differential carrier breaks and "thick" ring and pinion gears.
3.55 and 4.10 Gears Variations - Learn why some gear ratios have variations between some axles and brands.