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Wednesday, April 5, 2017

Five Easy Steps to Select the Correct Universal Joints and Shafts For Your Steering System

Filed under Tech Tips


What makes Flaming River unique is that we have designed a complete steering system from the steering gear, to the universal joints and shafts, to the tilt steering column, and even to the steering wheel. Let's say that you've got your steering column selected, and you know what kind of steering gear you're planning to use. Now what? Now is the time to put a little bit of thought into figuring out how you're going to connect the two together using universal joints and shaft so that you can actually steer your vehicle. Read below for five easy tips for designing your steering system, and how to select the universal joints and shafts needed to complete your installation.



1.  Determine whether you will need a two or three u-joint system. This will be dictated by the angle of the universal joints and the routing of the column to the steering gear. If it’s a relatively straight shot, and your universal joint angle will be less than 30°, then you can use two universal joints and one piece of shaft.


If you need to use two pieces of intermediate shaft to route around an object such as your headers or exhaust, or your universal joint angle will be greater than 30-40°, then we recommend a three u-joint setup. If using a three u-joint system, a support bearing or support bearing kit will be necessary and can be used with either splined or DD shafts. Your center u-joint in a three joint system will be either 3/4" DD X 3/4" DD or 3/4"-36 X 3/4"-36, depending on the type of shaft that you select.


three u-joints with shaft assembly and support bearing



2.  Choose the type of intermediate shaft that you will be using. We offer 3/4”-36 splined or 3/4" DD stainless steel shafts. The style of shaft that you select will determine one of the yoke ends that you need on each universal joint. 3/4"-36 splined shafts have two inches of spline on each end and can easily be trimmed up to 1” on either side. 3/4" DD shafts are available in 18", 22", or 36" lengths and can be cut to an exact size.

3/4" DD and 3/4"-36 splined shafts



3.  Determine what yoke ends you will need on either end of your universal joints. To determine the size and shape of the other yoke end of each universal joint, use this reference application chart to select the correct universal joint to connect to your steering column and your steering box or rack and pinion setup. If the chart does not list your application, identify the shaft shape using the diagram below and then measure the diameter using calipers or a micrometer. 

steering shaft yoke sizes and shapes

 If your shaft is splined, count the total number of teeth (i.e. 1”-48 or 3/4"-30). If your shaft is DD ("Double D" – it has two round sides and two flat sides), measure the diameter across the rounds—it will most likely be 3/4" DD or 1” DD.


Note: We do offer a number of different universal joint installation kits that will allow you to connect a Flaming River column with a 1" DD shaft to popular gear box and rack and pinion designs.



4.  Select the appropriate length of intermediate shaft.  If you are using a 3/4"-36 splined shaft and two universal joints, measure the distance between the rack and pinion or steering box, and your steering column shaft. Take this measured distance and then subtract 3.25” and round up to the next whole number to determine which shaft length will be best for your setup. DD shaft can be cut to size and multiple lengths can be cut from one piece. Ordering a larger size than you think you may need will give you a safety net in case you need to re-cut or adjust your steering linkage prior to installation.



5.  Use dowel rods to mock up your system prior to ordering.  If you are using a three-joint system, we recommend that you first use 3/4" dowel rods to mock up your system. This will allow you to experiment with different shaft lengths and universal joint angles. Once you’ve mocked up the design of your steering linkage, we recommend 3/4" DD shafts, as they can easily be cut to the correct length(s).



Other Important Notes for Proper Universal Joint Installation:

  • NEVER WELD a universal joint unless it specifies that it can be used in welded setups. You can refer to our universal joint specifications sheet to see which product lines can and can’t be welded.
  • Phasing – Keep the forks of the yokes closest to each other in line, and parallel to the center of the shaft, to avoid binding.
  • When inserting a shaft into the universal joint, make sure that it goes in 7/8” and is flush with the yoke end. A shaft that does not fully engage with the yoke can compromise the strength of the connection. However, a shaft that is too far into the yoke will cause the shaft to interfere or bind with the operation of the u-joint.
  • Set screws are supplied on all universal joints that have yokes that are splined or DD. However, it is necessary to dimple the shaft to properly secure the set screw. Loc-Tite or thread locker should also be used. Set screws should be periodically inspected and checked for tightness. Watch this quick video for more information on how to safely and properly install your universal joints.


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