1980 F100 Rear End Alignment Troubles

Hey there! It sounds like you’ve been doing some great work on your 1980 F100. That offset issue can be a real head-scratcher, but don’t worry, we’ll get to the bottom of it together!

Since you’ve already confirmed that the bed is centered on the frame and the perches are aligned on the axle, let’s explore a few potential culprits:

1. Axle Housing: Sometimes, the axle housing itself can be slightly warped or bent, which could cause an offset. Make sure to check it thoroughly for any signs of damage or misalignment.

2. Leaf Spring Alignment: Even with new leaf springs, if the alignment isn’t perfect when they were installed, it can lead to the axle being off-center. Ensure that the spring bushings are seated correctly and that the springs are installed the right way (and that they match in size and specifications).

3. Shackle Placement: You mentioned swapping out the shackles. Double-check that they’re installed correctly and are the same length as the originals. A difference in shackle length can affect the positioning of the axle.

4. Frame Issues: It’s also worth inspecting the frame itself. Sometimes, frames can become twisted or damaged over the years, which could lead to an offset rear end. Look for any signs of prior damage or repairs.

5. U-bolts and Torque: Make sure the U-bolts are properly torqued. If they’re too loose or improperly installed, they can lead to shifts in the axle’s position.

6. Tire Size and Pressure: While this is less common for causing an offset, ensure that your tires are of the same size and properly inflated. Sometimes, uneven tire pressures can give an optical illusion of misalignment.

If you’ve gone through all that without finding a solution, you might want to take a look at the suspension setup more closely. Sometimes, it’s beneficial to get a second pair of eyes on it, so if you have a buddy who’s handy or even a local shop familiar with vintage Fords, it might be worth asking them for input.

You might also find some useful discussions about similar issues on the Bullnose Ford subreddit or in the Ford Trucks Forum. They can be real treasure troves of information and support.

Let me know how it goes or if you have any other questions! Happy wrenching!