[Jim Huseby]

Here's something which will tell which corner is sagging: (1)Park the car on a level concrete surface and make sure you have matching tires all with the same tire pressure. (2)Measure and record the heights of all 4 fenders at 12:00 o'clock. (3)Place a floor jack under the exact center of the differential (use plenty of padding to keep from chipping the paint and to allow the center section to rock) and raise the jack until both rear wheels are clear of the floor. (4)Re-measure. If the car levels out, then the rear spring or crossmember is at fault or the frame is twisted. (5) repeat steps 3 &4 but raise the front instead of the rear . You may find problems with one or both springs or crossmembers. The frame could be twisted, also. In un-restored or poorly restored cars all three problems are likely. Has anyone done it this way? You can also check the frame for twist and/or fractures in the crossmembers this way by measuring the vertical distance of all four corners of the frame to the floor with the rear of the car raised because the the front springs will hold the front of the frame still and the rear, being supported in the center, will allow the frame to do its twisting un-influenced by the rear spring. Even though the front may lean to one side or the other, just measure the vertical distance to the floor from each front corner of the frame and check if the rear corners vary the same amount. By doing both of these tests and comparing, you can also determine if the crossmembers are cracked/broken. You can inspect the front crossmember for cracks or distortion by visually inspecting it with the hood open if it is perfectly clean. The rear crossmember can be best visually inspected if you have a removable bread pan.