What is the Angle Between the Trailing Arms

[NICK3757]

Hi All. I'm looking to see if someone knows what the angle is between the trailing arms on the 60-72 trucks.

I'm looking to draw up some axle perches to be cut and bent so I can use a Dana 60 on my next project, but I don't want to open up a set of perches with a grinder to fit the larger axle tube.

[franken]

Maybe there's an easier way, but this nonsense is what comes to mind
If you can get some precise measurements of distance it would be easy to calculate. The trouble is precision w/ an old truck.
Picture looking down from above at the trailing arm in place. Think of the slash / as the arm. There's a certain distance vertically and one horizontally to make a right triangle /_|. If you can get those lengths, the rest can be calculated. Do the same for the other side and add the 2 together to compensate for a bent frame if needed.

Maybe the bigger "pic" is more clear. The vertical line is the frame, the angled one the arm, and the bottom the axle.

/|
/ |
/__|_

Something like sine(Diff/Frame) will give the angle between the frame and the arm. My math is rusty so don't trust me.

[franken]

Might need to add some spaces or remove underscores to make that look like a triangle...

[NICK3757]

I went out to the roller I'm planning on using and took some rough measurements going off of the centerline of the trailing arms. Using the rough measurements I made, and drawing them up I got an included angle of 31.43°. I don't think the engineers at GM would go with an odd number like that, so I'm thinking that a 30° included angle is what they're supposed to be.