Search
Filters

Understanding U-Joints

Understanding U-Joints

When building a custom street rod or muscle car with driveline components from multiple sources, it is not uncommon to encounter u-joints of different sizes. Because your vehicle is now a custom application, going to the local auto parts store and looking up a u-joint by year-make-model won't work. But don't despair; with some simple measurements, it's possible to determine the required u-joints.

 

Most common driveshaft u-joints applications will use outside locks, where lugs (image 1) or snap rings (image 2) are used to secure and align the u-joint caps in the yoke.

 

 

Determining the u-joint series for external lock applications is a simple matter of measuring a few critical dimensions.

 

Measuring for Driveshaft U-joint Fitment

If you don't have the u-joint

1) Measure the distance between the lugs of the transmission and pinion yokes and the distance between the snap rings of the driveshaft yoke to attain the overall widths

2) Measure the yoke gap and the diameter at the cap location to get the cap diameters.

Make sure to check all of the width and diameter dimensions, as they may be different. If the dimensions do not match, you may require a conversion u-joint.

 

If you have the u-joint

1) Measure the outside distance across the u-joint (with caps installed)

2) Measure the diameter of the caps

Make sure to check all of the width and diameter dimensions, as they may be different.

 

Standard u-joints sizes are classified by series, with each series having specific cap diameter and overall joint width. Typically speaking, a higher series number translates to a stronger joint.

 

Standard U-joint Series, Dimensions and Part Numbers

Series

Cross Width

Cap Diameter

Spicer P/N

1310

3.219 (3 7/32”)

1.062 (1 1/16”)

5-1310X

1310BC*

3.219 (3 7/32”)

2 @1.062 (1 1/16”)
2 @ 1.125 (1 1/8”)

5-7439X

1330

3.625 (3 5/8”)

1.062 (1 1/16”)

5-1330X

1330BC*

3.625 (3 5/8”)

2 @ 1.062 (1 1/16”)
2 @ 1.125 (1 1/8”)

5-7438X

1350

3.625 (3 5/8”)

1.188 (1 3/16”)

5-1350X

*BC denotes Big Cap, a Ford creation with two thicker caps to resist the deformation caused by over-torquing of the u-bolt straps.

 

Conversion or combination u-joints include a mix of two different series specifications in the same joint so that that mismatched yokes and driveshafts can be connected. The caveat is that the joint is only as strong as the smaller series.

 

Conversion U-Joint Series, Dimensions and Part Numbers

Series

Cross Widths

Cap Diameter

P/N

1310/1330

3.22 (3 7/32”)
3.625 (3 5/8”)

1.062 (1 1/16”)

Spicer
5-134X

1330/1350

3.625 (3 5/8”)

2 @1.062 (1 1/16”)
2 @ 1.188 (1 3/16”)

Spicer
5-648X

1330BC*/1350

3.625 (3 5/8”)

2 @1.125 (1 1/8”)
2 @ 1.188 (1 3/16”)

Neapco
2-4953

 *BC denotes Big Cap, a Ford creation with two thicker caps to resist the deformation caused by over-torquing of the u-bolt straps.

 

Strength Ratings

 

U-joint strength depends on many factors, including material type, body design, the presence of a zerk fitting, cap size, etc. The chart below summarizes the continuous lifetime operating torque and yield torque values (the point at which the u-joint begins to deform)

 

U-Joint Series Torque Ratings

U-Joint
Series

Continuous Lifetime
Operating Torque

Yield
Torque

1310

130 lb-ft

1,600 lb-ft

1330

150 lb-ft

1,850 lb-ft

1350

210 lb-ft

2,260 lb-ft

 

U-Joint Strap Kits

U-Joint
Series
Width 
Center/Center
Torque
Specifications
Currie
Strap Kit P/N
1310/1330 1.416 in. 14-17 Ft-Lbs CE-4058
1330 BC* 1.590 in. 14-17 Ft-Lbs CE-4059
1350/1410 1.666 in. 20-24 Ft-Lbs CE-4060P

 *BC denotes Big Cap, a Ford creation with two thicker caps to resist the deformation caused by over-torquing of the u-bolt straps.

 

Leave A Comment
Comments
1/22/2020 8:39 PM
Excellent enlightening information.....thank you very much for your effort to compile this info
Jimmy
5/30/2020 2:05 PM
Great info helped me out
Categories