E-Body rear frame rails installation

[71cuda#match]

I bought the rear frame rail stubs that go from the top of the wheel well to the shackle mounts for my 1970 Cuda rebuild.   I copied the FSM frame dimensions, and used the plumb bob and made my marks on the floor.

First I measured the horizontals from the lower outside front shackle mount (Rear facing side) to the center of the rear shackle mount tube and got 56.5 inches.  Great.

My problem is when I do my diagonal measurements I get closer to 44.5 ".  The FSM diagram shows 46.06".  Again I am measuring from the lower outside front shackle mount hole to the opposite outside rear shackle tube center.

Is the field service manual a misprint?   Am I doing it wrong?

Confused

[Tunis]

Hi,

Where did you find 46.06? I can not find it in the FSM? I can see 76.06 diagonally at the rear frame rail from outside of the shackle on one side to the upper inner? hole on the leaf spring front mount on the other side.

[71cuda#match]

OOPS  !     Excuse me, diagonally i get 74.5", not the 76.06" in the FSM diagram.   I mistyped.

Mike

[Tunis]

I see and sorry for pointing that out. Are both diagonals equal length? If that's the case, and both horizontals are correct length, then the unibody must be too narrow, right?

[71cuda#match]

Tunis,

Thanks for your reply.  I don't think I can gain enough to get 76.06".  I still think that is irregular.   I plan to attach the rear crossmember to the rail ends and remeasure everything.
A fresh start is always good, for new perspective.  Thanks for your input.

The horizontal measurements are spot on.

I just wonder if I should be measuring from the front side of the leaf spring attachment plate versus the rear side.  Any thoughts?

Mike

[Tunis]

Sorry I can't be of more help.. Where is everybody?

It looks like the measurement for the horizontal and the diagonals are in the same location 'E'. If the horizontals are spot on now then you should be measuring from the correct location.

If I look at the FSM now, I would say that 'E' is the outer top hole on the back side of the spring attachment plate. And I think that makes sense, because if you have torque boxes, the boxes will not allow a straight down measurement at that location.
It's too bad that the FSM doesn't have any measurement in width at the rear of the vehicle.

Another measurement you can verify is the 150.49 - diagonal from rear k-frame bolt to rear spring shackle. If that is true, then I would say that your frame rails are in the correct spot. And again, if your diagonals in the rear are to short, your horizontals are spot on, then the distance between the frame rails are to short. Are the front spring attachment plates originals?

Per