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Street Race Truck More... The Toolbox

U-Joint Selection and Design

Tags: Tech, Steering
Mock Up

The steering system is often designed late in the build process. In a lot of cases it’s best to mock up the steering when the engine and exhaust components are installed. Positioning the column, steering shafts, and u-joints early on with respect to the engine and steering box will ensure that you select the correct parts. Steep angles and limited space may require a little trial and error to achieve the correct geometry, but with a little ingenuity and careful measuring, it can be accomplished.

U-Joint Selection

In addition to our application charts, you will need to determine the spine size on your steering component. Whether it’s a rack and pinion, steering column or steering box, measure the outside diameter and count the number of splines. On some components there may be a flat spot or keyway on the shaft. In this case you can lay a straight edge across the top, or count half the diameter of the splines and double that number. We would then know how many teeth are in a theoretical full circle.

Speedway's Available U-joint Combinations:

  • Smooth bore on both ends
  • Smooth bore to splined or double D
  • Splined and/or double D on each end
U-Joint Angles

If a single u-joint is installed we recommended not surpassing a 35 degree angle. This can cause hard spots in steering or premature wear on the joint bearings. If the u-joint angle exceeds 35 degrees consider a double jointed u-joint like PN 910-3247.

Shaft Support

Anytime the steering system has more than two universal joints installed, it’s recommended to use a steering shaft support, like PN 175-0757. It’s best to install the support as close to the center joint as possible, or if one shaft is significantly longer than the other, it’s best to provide support to the longer shaft.

Double D Shaft

A double D shaft has two flats on the shaft that correspond to the female end of the u-joint. For example: the 3/4-inch measurement on a double D shaft is measured across the rounded portion of the shaft. To strengthen the connection of the DD joint to the shaft, you can drill a dimple on the steering shaft for the set screw to clamp to. Simply tighten the pinch bolt to make an indentation and drill 1/8-inch recess where the pinch bolt will tighten. A dab of Loc-Tite on the set screw is always good insurance before finishing.

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