There are many different ways to square the rear end depending upon mechanical preference and comfort. This is one popular technique utilized by many professional teams.
Place the rear end in the chassis and bolt up the torque tube. Set the axles on 6 blocks if its a standard chassis, 5 on the left side and 6 on the right if its a raised rail car.
Secure the birdcages with spacers and the wheel nuts. Measure the distance from the rear round machined portion of the torque tube to the outer edge of the chassis by placing a straight edge vertically against the frame.
Center the rear end by equalizing this distance on both sides of the car.
This distance should measure between 10 1/8 and 10 Ό. Now with the rear centered side-to-side, start with the right side and measure from the leading edge of the rear axle to the front edge of the motor plate.
On a 39 car this measurement is 37 5/8, 38 5/8 on a 40 car. Roll the axle forward or back on the blocks to achieve the correct distance.
Once you have secured that distance on the right side check the left side. Ensuring that the rear is still centered in the frame and the right side measures correct, the left side may vary by as much as 1/8. This is generally left to lie as is.
With the radius rods connected, place a level on the flat bottom portion of each bird cage and adjust the rods so that each cage is level with the bottom frame rail.
Now bring your rear arms up to each bird cage flag and adjust each rod end so that the lower bird cage bolts slide freely through the cage and the rod end. Having completed this, recheck all of your measurements to ensure that nothing was moved during the previous processes.
If all measures correct bring your jacobs ladder to the rod end or clevis and adjust the rod end or clevis in or out so that the bolt also slides freely. With these operations complete check your work by ensuring the torque ball is free and the jacobs ladder is not bound.
Now you are ready for race height setup blocks and stops.
Squaring the Front Axle:
Set the front axle on 4 set-up blocks, or 3 and 4 if it is a raised rail car. Offset the axle 1 to the left side by adjusting the sway bar. This gives clearance to the left front torsion arm and combo steering arm.
Measure 13 5/8 from the center of the right front torsion tube to the center of the axle on both sides.
After roughing in the radius rods to this measurement, measure from the leading edge of the rear axle (still on 6 blocks) to the rear edge of the front axle on the right side.
After having gained this measurement we will set the lead.
Check the left side the same way and adjust the rod length so that the left measurement is equal to or up to Ό set back depending upon driver preference and size of track.
With the axle now square we can adjust the caster. Place an angle finder on the right front steering arm.
Adjust the top right front radius rod so that the angle reads anywhere from 6 to 10 degrees. Again this is driver preference, some drivers like more positive feel in the front end than others.
With this complete you can drop the axle down to race height set-up blocks and adjust the stops. Dont forget to set the tow. An 1/8 of tow out is generally the norm.