Measuring your driveshaft

Whether it's restoration of an old classic, or the manufacture of a racing or drag car, taking a measurement for your new driveshaft is an important step in the process of building up your project. Getting the measurement right is critical to the future performance of your vehicle.

Measuring a single piece tail shaft

Let's first look at the single piece driveshaft with a conventional slip yoke at the transmission and an open yoke at the diff.

First and foremost, the installation of the transmission and differential must be completed, only then can you take a measurement from the output seal of the transmission to the face of the diff yoke (equal to centre of the universal cap) as shown.

Measuring a two piece tail shaft

First, measure from the transmission seal (A) to the centre line of the centre bearing mount (B), then from the centre of the centre bearing mount to the flange face on the diff on flanged models(C), or the 'face' of the diff yoke (equal to half way through the uni cap) on open yoke models(D).

Different types of Diff yokes

Ford 9" Diff Yokes

To identify yoke type and size refer to picture 1. Measure the width between locating lugs (A) and the width from U'Bolt hole centres (B). A can be 82mm or 92mm and B can be 35mm or 40mm. This will identify the size of the yoke. The universal joint is located in the yoke between the lugs at each side and retained in the yoke by U'Bolts, as in picture 2

 

Picture 1

 

Picture 2

Borg Warner and STD Diff Types for Australian and American Cars

The main difference with these diff yokes from the Ford 9" is that the universal is located by circlips inside the shoulders of the yoke. Vehicles in this group are all the original Holdens and Toranas up to the Commodore series. Universal joints fitted to these yokes always had circlip grooves in the caps (see below)